400's are they any good?

The problem with B block 400 engines are;

Low compresion, dead low.
Broom stick cam

Valve sizes are small, but! They are good for the size of the engine unstroked as the allways quick mention is to do with these things is. And not a bad idea ethier. A 451 or 500 ci stroker kit is a on the shelf item.

They come with the everything the 383 is famous for (Except above) plus a few more inchs. If a on the cheap hop up is the goal, you'll need to mill the heads down some for a decent ratio and install a cam/timing chain in it to get ya going.

If a TQ aint the carb for you (850 cfm size perfur'd) then look at a 750 cfm squarebore size to start. Equip as normal, like any other engine.