Originally Posted by killbucket
I do know that you'll want to replace the entire front suspension- modern brakes would be a must.
There is nothing wrong with the stock suspension that a few bolt ons will not fix. Rustyhope
sells a bolt on disc brake kit and then a change of the upper shock mount to the frame rather than the upper A-Arm (I think Rustyhope is selling these kits as well now) and you are good to go with an otherwise stock rebuild. If you want to go this route there are also rack / pinion kits and dropped spindles available from Fatmans. The old Mopar front suspensions were actually ahead of their time compared to the other makes at the time and other than the upper shock mount were a pretty good design. My 48 with the discs kit installed is my daily driver in Dallas traffic and I have had zero issues with it.
This is my second 48 and the first had a Nova subframe professionally installed. Quite frankly for the cost involved and the down time, I don't notice that great a difference. Especially when you consider that you will still have to rebuild the new front suspension before you can get it on the road.
You can fairly easily install a small block Mopar by offsetting it about 1.5 inches to the passenger side to clear the stock steering box or better yet go with the rack / pinion.
My choice was to stick with the flathead in my 48 Plymouth coupe. These engines were produced by Chrysler up into the late 60's and used in various industrial applications so most parts are available from Napa. There is also a small aftermarket "speed" parts market around the flathead Mopar. Dual Intakes, Headers, Aluminum Heads are available new or you can hold out to find vintage ones on EBay fairly regularly. The vintage stuff pricing can go pretty high so for me the new stuff was the way to go. Langdon's Stovebolts
and Edgy Speed Shop
are good placed to find "speed" parts and Edgy regrinds cams as well.
There is also a kit on the market to bolt a T5 five speed trans from an S10 pickup to the flathead or you can look for an old Borg Warner R10 overdrive from a mid to late 50's Plymouth/Dodge. The R10 is a direct bolt in swap if your car had the original 3 speed then just add a couple of wires for the controls and you are good to go. I had installed the R10 in my 48.
Here are a couple pictures of my flathead and a picture of the new Edgy aluminum head that I have yet to install. The flathead gets folks attention among the sea of small blocks at a show.
Also you will want to register over at the P15-D24
site there is a ton of info over there for these old Mopars.