i'd think weight would come into play here also, 496 stock block vs a 499 dart block, is 100lbs more. Not sure what the weight limits are or if that matters with pulling tractors or not

Really wouldnt matter still have weight to play with anyway. Would probably go with the dart block either way.

showdown496 I have a set of 990 heads on my 468 rite now making about 800 hp....they are ported to the max..also have a victor intake that is port matched to the heads..I have a mud racing truck and they changed the rules this year so I can run alluminum heads..willing to make trade or sell outrite..if your iterested give me a call at 318-613-6632 if it goes to voicemail leave name and # and I'll call you back...thanks Chad