Aside from heat treated seats what's the difference between 906 and 452 heads?

[bull]

Aren't they pretty much the same otherwise?

[mopar_nut_440_6]

Yes they are pretty much the same.

IMHO the best open chamber head is the 452 casting, which was produced from 1976 through 1978. These castings offer the same combustion chamber design, flow, and performance potential as the 906 castings, but they already incorporate hardened valve seats, making them very tolerant of today's unleaded fuels.

Cheers