I am the proud new owner of a 1967 Oldsmobile Holiday Sedan Hardtop. The car has the stock 425 and a 4-bbl carbuerator; I have heard that there 360hp and 375hp versions of the 425 4-bbl, can anyone tell me how to determine which version I have?

 

The two versions were actually the 365 HP L74 motor and the 375 HP L75 motor. The main differences were compression ratio and single vs dual exhaust. If the engine was originally a single exhaust, it's the L74. If it's been converted to dual exhaust, the only way to know for sure is to look at the pistons.