I can fax you the engine specifications as published in motors circa 1968 thru 1974. 1968 375 hp V8-428 4 bbl 4.120x4.00 10.50 375 @ 4800 445 @3600 (torque) 1968 390 hp V8-428 4 bbl 4.120x4.00 10.75 390 @ 5200 465 @3400 1969 360 hp V8-428 4 bbl 4.120x4.00 10.50 360 @ 4600 472 @3200 1969- 370 hp V8-428 4 bbl 4.120x4.00 10.50 370 @ 4800 472 @3200 1969- 390 hp Vby CHARLES GRACEY - Pontiac GTO Forum