There isn't really all that much crossover with Top Sportsman and Top Dragster. Most of the cars in those two classes are boosted or big CI (often on spray), so we have more in common with Pro Mod than Pro Stock. A rolling PS car can be used in TS, but regarding engine and transmission, there is very little PS left in it by the time it's a competitive sportsman car.* The logical trickle-down would be for those parts to end up in Comp, but between rules differences and the small number of classes anyway that use PS-like components, I don't imagine the demand would be all that high.
*This refers to NHRA Pro Stock. There are several TS cars now that could utilize parts from the Mountain Motor version.