Hello M.D
I like the 400 make good torque.
383 makes about 15-20 hp & 35-50 ft.lb less torque than the stock 400 with 5.7 rods use 350 rods lots of pistons combo- (stock are 5.565 for the 400) either of these combo is not to bad on price $1000.00 up depending on parts.
My preference is 400 .30 over block with a 3.875 stroke 6.00 inch rods = 420 cu. in.=about $2000.00 for the rotating ass.(depend on the crank and pistons) this is a mouse that thinks it is a big block
( I have one)
The key to it all is the HEADS try to stay around 215cc intake ports with the 383 - 400 should make good hp in 5000 6200 range with good low end torque.
Some say the 400 heats bad but there a couple easy fixes for that
The 377 destroked 400 (use 350 crank in 400 block) is like the 283 or 327 (only big cu.) and will wind fast and shut down quick make Hp but no torque good IMCA motors most turn them 7500-8500 big $ in reliable parts for them.
E-Mail me if you like, have played with these quite a while and have spent more $ than sense
If you like I can run some desk top dynos for fun.
Ken