have a set of blown 502 in a 46 foot boat.4 in street car the rest all in drag cars or mud racing .most of the time if custom roller i will do the 4/7 swap its about the same price .i seen were some say theres a gain with them all of the stuff i build seams to run good no phone calls .not one of my customers had dyno sheets with two cams with one with the 4/7 swap and other stock .for a all out effort it may be EZ on parts. small gain on hp and tq .Erson stocks alot of shelf 4/7 grinds so there not allways customs if you find something that works for the job