Marine 273 build

OK, so I think Im close with my compression ratio calculator, as long as my assumptions are fairly close.

I assume I would be going from:
bore = 3.625"
stroke = 3.31"
head gasket bore = 3.75"
head gasket thickness = .030"
combustion chamber volume = 68cc
piston dome volume = 0cc
piston deck clearance = .012
compression ratio =8.4:1

And assuming I can get a set of 302's down to ~60cc, either by being lucky and finding a set with small-ish chambers, or a bit of milling, Id be going to:
bore = 3.625"
stroke = 3.31"
head gasket bore = 4.08"
head gasket thickness = .021"
combustion chamber volume = 60cc
piston dome volume = 0cc
piston deck clearance = .012
compression ratio =9.4:1

If that is in the ballpark, I'd be happy. Of course, I wont know some of those numbers until the old heads come off and new ones cc'd.

Yes, it definitely is tough to get compression out of a short stroke, small bore motor!

Yes, I understand that milling the heads has consequences in terms of valve train geometry and intake fitment. No sense in getting too far down this path until I get a set of heads (302's or otherwise) in hand, to determine the chamber size and what they need for clean up- and then I will need to have a conversation with my machine shop.

My capabilities? Everything short of doing the machine work, pretty much. Assembly is no problem. I am not afraid to try porting on my own, but time would most likely be a limiting factor.

What do I want to spend? As little as possible! I know what most of the pieces will cost- heads, springs, cam, intake, bolts, gaskets, etc. I want to say my shop charged me about $300 for the last set of heads I had done (clean up, valve job, etc). I assume this set would run similar or slightly more, depending on how much extra machining was required. I do not know what it would cost to have a set of heads ported, if I decided I didnt have the time. Are we talking $200? $500? $800? How many hours would it take me to tackle the heads on my own? Say just the basics- port matching and general smoothing?

The nice thing is that I have no time table for this project... it could happen this winter if I really wanted to push it, or I could slowly start collecting parts and do it next year. Its never too early to start planning.