Larry Morgans son did race in B/A with the small CI pro stock Hemi, I watched him last year at Norwalk. They sold the car and engine to Buddy Perinson who raced it at the end of last year. When Larry raced B/A it was with a 500 CI pro stock hemi and he had the record at 6.95 I believe. B/A is 5.4 per CI so a 500 CI car is 2700 LBs. The small engine car was appox 2450 per the rules. The pro stock blocks start out at 4.680 and are over 4.700 today. Dont think you can run the bore that small with the valve locations they use. Larry has some of the older head casting raw that may work with smaller valves and different valve locations. The only way to sleeve the bores smaller is with a sleeve that registers at the top like a aluminum block because of the block design. They are dry sump engines so you would need a single stage external pump and a one off oil pan, the cam tunnel is closed also with not much drainback. Larry told me they didnt spin the little engine any higher than the 500 at the time. They are cool engines for sure and not for the average guy. Would be a very expensive engine to build, for instance the rear main seal costs 65.00 and so on.