The #48 casting heads on a 350 HO had a smaller combustion chamber than the 1969 #48 heads they used on a 400. I have worked on both sets of heads. Pontiac only offered 3 different camshafts for that year and the only real differences were in duration not so much in lift so it was really the RPM range of the engine.
Compared to today's camshaft grinds the HO,RA3,RA4 were really in the stone age as far as how the engine runs.