Are you sure the heads are “183”? Could they perhaps be “188” more specifically, 3927188? If so they are a so-so stock head with 1.72/1.5 valves and 74cc.

The 400 heads you have are probably 3961598 or 3973493 (most common numbers for 400’s). They are not much better, i.e., 1.94/1.5 - 76cc.

Did you have the block decked when you had it bored? If so, what’s the deck height?

The stock height of an uncut 350 is typically 9.025" from crank C/L to the deck.

The compression height of a 350 piston varies by manufacturer (anywhere from 1.53 – 1.56) which will influence the compression ratio.

A bit more info would be appreciated..

Regards,
Glenn