I recommend soild flat tappet. Engine in my Lebaron makes 800+ HP with a Racer Brown STX-22--.590" lift x 276* dur. at .050. 2600# car with 512 RB and Indy SR heads. Been 5.44 at 127 mph. 1100+ run and on second set of springs, comp cams 928-16, $160 for springs, not $350 like for a roller. Same cam in my sm block Demon, Close to 2200 passes and on 3rd set of springs, same cam and lifters. Shift both cars at 7000 rpm and will go higher if needed, 8000 high side chip and hit it from time to time in water box. 160# seat and 350 open. Call Jim at racer Brown. 410-866-7660. STX-22--.590" lift--276* at .050. Let Jim set the LS to match your combo.