Which block are you using, standard, RR or A-1? the standards have a open slot between the mains and the bottom of the cylinders, not a good choice for high HP or high RPM The RR and A1 will have those initials cast into the top of the lifter valley and the edge of the deck, usually on the rear passenger side, thier supposedily better castings with more meat in the block Let us know what you find A lot of the old time racers like to use the 354 blocks to build do to the problems with the 392 blocks the 1955 and 1956 heads are better also, better port angle to the valves, just install the size valves you want to run in them