You want to find look for
reproduction full stock HP compression 383 pistons
like the 68-69 335hp RR/Super Bee 383 engines etc.
org. style that are 1.92" compression height,
were just less than 10.5:1 as advertised,
with 0.020" steel shim head gaskets
on 906 casting open chamber heads
But;
remember if you use a 0.038" thick head gasket's,
like most Victor or Felpro etc.
or a much larger bore in the gasket like 4.40" etc.
like many 'over the counter' hg's are (on a 4.25-4.310" bore)
it's even less compression on-top of that
(try to get some with a smaller bore closer to the bore size
that isn't hanging over into the cylinders)
especially with open-chamber 906 castings
or other castings of open chambered heads
A good proper bore & thickness gaskets are NOT cheap,
like the parts stores std Victor or Felpro etc.
expect to pay $75 'each'
Cometic Head Gaskets is a good source,
MP used to be, but they are even more $$$ like $80+ each
Something with around (middle of the road) a
1.908" compression height
to be sort of like the performance 68-69 383 engines
or any of the HP 383 with open chamber heads
& "advertised" as 10:1 with a 0.020" steel shim gaskets,
they still weren't/aren't really 10:1, more like 9.5:1 to
(maybe stretching it at 10:1)
depending on how much the heads & block have been surfaced
or if the block is squared/decked properly, not more than 1 line bore
(that moves the crank upwards a light bit too)
a lil' more compression with closed chamber heads & thin 0.020" steel hg's
you may have pistons with a 1.868" ch's,
low performance 383 pistons, off the shelf std. replacement parts,
not like OE or any performance applications
usually cast with multiple valve reliefs too,
leaving the pistons farther down in the cylinders at TDC
way down on compression & then add a thicker off the shelf gaskets
& open chamber heads & it's lower compression, at that point
if that makes any sense
