There exist a goldmine of used "PRO" racing components ( some of which are slightly used and abused ) but in my opinion are often usable in upper HP Bracket cars for less investment than new state of the art alum 572 wedge motors..... with a couple of major considerations :
(1) limited or no cooling - therefore alcohol is the only feasible fuel , but is there a better fuel for bracket/drag racing ( cheap , more HP, and runs cool ) An exception to this is here , some other old blocks can hold water also, but used heads with water jackets are hard to find and new ones are expensive --- INDY, MOPAR
(2) Every possible dimension of a used block, head , cam, ....etc. is probably different. Since a custom made component costs no more to be designed differently than stock and ever pro application is probably different than the design criteria of the the original mopar engineers , assume that it is.
(3) Use your head, if a veney head has been sized for 9/16 studs, a 1/2 stud block will work, if the right size washer (stepped washer) is used.
4) Ask questions , (all of the questions) for a block the minimum info you need is - a) alky or fuel b) Manufacture and Series - ( tfx 96, KB stage 5) , c) Deck Height - it can vary over 1/2' from stock d) Head Stud size and length - some heads used much shorter center studs because the didn't go threw the rocker stands e) crank journal size - 3" is common e) what heads were used originally - Veney and BAE , short deck TAD motors had a different configuration for the seal on the ends of the intake, but in this case an adapter can be made to reconfigure the block . f) Cam Position - most camshafts are raised for additional rod clearance. g) Camshaft Diameter - several to chose from h) Oil Pan - many bocks do not accept stock i) gear drive - tfx has its own , and raised cam blocks use one that may be stock looking , but slightly taller
j) Bore Size - and this means inside and outside of sleeves, fuel blocks are usually 4.187 inside diameter allowing for smaller outside diameter , resulting in more material between the sleeves for strength. They can easily be bored to 4.310 , ( a 3/4 stroker gives you 525 inches).... but the block also supports larger strokes , if you chose a raised cam version
Example of a TFX 96 Block, the bottom of this block is much wider and shorter than a stock 440/hemi ( lighter, easier to work on and hopefully less damage to block when rods try and hurt it ) also the crank and main caps hang below the pan rails much like a BB chevy, note 2 bolt mains (2 more on sides- tie bolts,) some blocks have as many as 6 bolts or studs on 1 main cap