I had a 5700lb 74 c30 with a 383 making maybe 350 hp.
But I had 5.13 gearing in the thing. This allowed me to dump the clutch in 3rd(1.7) and hold it to 5500 before shifting into 4th.
I have lost several sbc engines. They can rev with simple mods and a shortened lifespan.
The last 383 I had I lost the rear main after cruising at 3800 for over a hour running 4.56 gearing.
You can run high rpm for hours if you build it right.
You need a good cooling system.
Your going to be stressing your oil gaskets so pay attention to those.
Expect 6mph going 80mph. Its a squarebody after all.
But all that being said a sbc USE to be easy to find and cheap to make 300hp with. The sm465 can handle 300hp all day long and a 14 bolt comes with 4.56 gearing.
Now the sbc are harder to find. So a stock 5.3 makes more sense if you want to run 5500rpm everywhere.
The 94 s10 money pit is running a stock 5.3, sm465, and a 9". The reason for the 9" is so I can swap 3rds out instead of axles. If I want power I will throw 5.xx gearing. If I want cruising then I can run gearing in the low 3's.
I am building it with room for turbos and a water intercooler. But Iam keeping the idea of running $500 200k 5.3 bottom ends and making a majority of the power with gearing in the rear.
This also lets you run a cheap(er) clutch then one that needs to hold 5,6,or 800 ft lbs.
If I get 10,000 miles out of a clutch thats ok because its only $150 or so. If that clutch is $700 then I am not going to be as mean to it leaving power on the table.
Guys may love overdrive or having 6 or 8 speeds. But all that shifting takes time.
Treating the 465 as a 2 speed using the 1.7 and direct(straight back) gearing allows for some nice times once you get a feel for things.
I have 4 or 5 sm465's at this point. They can be had for $50 to $250. Yes it is a heavy girl and yes it has truck gears. But the 2wd ones can take abuse. You can rebuild them yourself and they can handle axle twisting, torque.
If you do sheer the input on a 2wd its probally because the bellhousing HAS been broke or the transmission was pushed forward(jumping). Your going to break alot of other things before you hurt a sm465.
As far as length goes the 465 is often a winner, strength per dollar another win, using it as a 2 speed works with the right rear gearing, and you still have a burnout gear even if your running a 3.08 out back.
The thing is heavy, has a horrible gearspread, and is a toploader so you have a hole in your floor.
The fact you already have one(I think) or can throw one in easily leaves the rear axle. Now a FF14 bolt is a heavy axle. But it is built tough and comes with 4.56 gearing. You can ditch the drums and 4 steel wheels for a set of wide tires then weld the diff and you have a tough axle often for cheap. Still heavy mind you and your stuck with the 4.56 gearing. But the thing can handle clutch drops, a welded diff going around corners, and no need to upgrade the axle shafts.
Or you can just run a ford 9" or toyota axle then switch gearing that way. Just plan on upgrading the shafts etc.
Before you look at building a engine that is going to require premium fuel or e85 and require a expensive clutch look at making the power in the axle with gearing.