A 420 or 440 typically has a 66mm stroke crank. A 440 has a 69mm stroke crank so ,yes, there can be clearance problems but none that are insurmountable. Balancing any of these big block modifieds (390/420/440/460) can greatly help smooth them out and add reliability. Picking the elusive correct balance factor is the key. It typically involves adding weight to the counter balancers of the crank. Most all 460s have a larger 10 bolt side cover than the 390/420s. If I were going to build a modified 460 from Vegas Carts (other than Bullfrog Motosports, the only place I know to get one) I would spend the time and money to brace it well with added custom aluminum pieces and welding. Lots of welding. It adds cost for sure. Cost that seems wasted when it does let go ruining the block. To be honest, if the build is much more than "mild" I would brace the 420 block as well. I heard ARC is now offering a billet crank for the GX big blocks. Not sure of the stroke but it could aid in getting it balanced. Billet side covers add strength to thes builds also. I am not sure if a 10 bolt billet side cover for the 460 is available or not. If it is, I would consider it.
Consider getting a 450 or 500 cc MX style engine. They will have more HP and be infinitely more reliable and withstand way more rpms. JMO.
