[Kenth]

1969 XU is a 350 H.O. engine and used #48 heads as all 1969 350 H.O. engines did.

All 1969 400 "RAIII" engines used #48 heads, except Firebird YW code wich also was the only "RAIII"using the 067 camshaft and #62 heads.

Comparing #48/#12 heads with any #16/#31/#62/#13 head it is easy to see the difference of chamber size.