You will need everything from a v8 car. Rear axle, front spindles, steering box and then engine and trans. The 6cyl suspension is pretty different from the V8 suspension although you will easily find everything you need. Granada brake spindles I think are actually reproduced now so you can get disc brakes in the front while also converting to 5 lug

 

You could also pull a turbo 4 banger or a supercharged V6 from a Thunderbird

Definitely upgrade the suspension, rear and brakes

 

Welcome to Hotrodders... This thread was moved to the Basics forum where engine swaps are discussed. thanks

 

Based on my references, the chassis and suspension were redesigned in 1963 to accommodate the 260 (and later 289) V8. I assume you could make the same changes to your ‘61, but it would be a complicated job without a donor vehicle.

It might even be possible to swap all the parts in from a 1st generation V8 Mustang or the 64-65 V8 Falcon, since they were based on the Mustang body. However, there were quite a few differences between the V8 and 6 cylinder models.

 

The 6 cylinder car often had lighter duty steering suspension parts than later V8 cars. My 1962 Falcon when I installed front disc brakes required sleeves on the tie rod ends for the spindles I used from a mid 1970s Maverick.

As mentioned, when these car were factory prep for V8 engine in 1963 the trans tunnel and engine bay was opened up a bit for larger engine and transmission

 

This site will have all the answers you need to do the swap. Good folks over there.

COMET CENTRAL - Index page

 

Why not stick with a I6, maybe a 300 will fit? Less money, less work and plenty HP and on the road right away .

 

300 won’t fit that chassis. Way too long. 250 I6 would be the biggest, and it has a taller deck

 

The 61 Comet, Falcon inline is a structurally weak engine with only 4 main bearings. For 1964 Ford corrected this is sufficiency by redesigning the bottom end with 7 mains and within the same casting envelope enlarged the displacement from 144/270 to 200/250 cubic inches.

For a simple swap you want to locate a 1964 up engine these were used in the Falcon, Comet, Mustang, Cougar, Fairmont and a bunch of other models. If memory serves I think the 250 has a raised deck so it might not fit the 61 vertically.

Nothing wrong with a V8 but these early chassis weren’t designed for them so the cost goes up to strengthen the chassis and modify it to fit v8 components. Ford had their fair share of structural problems with the early V8 platforms that took till 67 to finally get worked out.

Bogie

 

You would probably be better off with a Mustang II type front suspension since you have to change nearly everything anyway. The six cylinder suspension would hold up reasonably well with a relatively light modern V-8. A mid 70s and later 302 doesn't weigh much more than the six, unlike an early 260, which is 80-100 pounds more than the late 302. The ball joint sleeves were needed because there was a change in the taper of most ball joints in the mid 60s. I've run into that swapping 80s parts onto a 60s Rambler. It was across the board, everyone (in the US) changed the taper angle at about the same time -- probably because most used outside suppliers for ball joints. This Heidt's kit says 60-65 Falcon/64-65 Comet, so you need to check on the differences. Earlier Comet might be more in line with the early Fairlane instead of Falcon.

The alternative has been mentioned -- 250 six (deck height was raised 1/8" over 144/170/200, so it should fit easily) or a turbo four/supercharged V-6. Even a 3.0L V6 from a Ranger along with the four or five speed auto (or manual!) trans would be a big power upgrade. Heck, a 2.3L Duratec would be about a 40% power upgrade! I'm putting one in a 61 Rambler convertible for that reason -- more of a cruiser, not a drag car. I want the "jump in and drive" modern EFI more than anything else, the power upgrade (and weight reduction) is a big plus though.

 

The Comet site has really great information on upgrading the 60/61 suspension system. The control arms are the same for 60 - 65 small Fords, including the 65 Mustang. The spindles for V8 cars will bolt into the control arms, tie rod ends from the corresponding spindles need to be used, the drag link from (I don't remember the model) is used, the source for it is also listed. A 65 Mustang box (V8) will bolt in to complete the upgrade. V8 chassis parts are reopped along with a brace that tied the lower control arm mounting points together under the engine.

Having said all of that, cost wise the upgrade is less than half the cost of the MII and is all bolt-in. I built a 66 Falcon Ranchero with a 302 EFI out of a Continental with a 5 speed. Wonderful driving car. Upgraded the suspension with most all the parts I've mentioned, the 8" rear out of a 67 Mustang (3.26) and the 5 speed gave just over 30 MPG on the road with a very nice "pull" from the stop lights!

 

I would suggest additional bracing from top center of firewall over to each shock tower (do they call that a "K-brace" ?)
And then use an aftermarket kit to make a cross brace between the shock towers spanning over the engine.

If you are going to V8, best bang for the buck on the rear axle is an 8.8" Ford.
The original '61 Comet rear is not going to last long, it is really light duty.