if you start with a box stock late 502 mag mpi, is there an al cylinder head that is a direct replacement bolt on that will give 9.5 to 1 compression ratio ( or there abouts) and use the original injection ?

You will need a head with about a 110-112 cc combustion chamber. If you get a head that is 118cc you can mill it down every .005- .006 is 1cc. Edlelbrock is the only one that I know of that starts with a smaller chamber.

Edelbrock's 110 cc alu head has an oval intake port which in turn causes a mis match with the intake. Their rectangular port heads does have 118 cc combustion chamber ...

so.... i need 110 cc ( give or take) chamber w/ rectangular ports... edlebrock has a lot of 110 cc heads ... not sure if any rectangular...

well the 110 cc number is what i needed to know specifically so am proceeding from there. thx very much tyler and alex.

i ve got one side with about 250 hours on it that has lost 200 revs off the top for no apprent reason... runs perfect otherwise in all respects... thinking maybe a valve spring but haven't really looked hard at it yet. plugs all looked good and the same when i had them out about 10 hours ago... could easily be something simple but just thinking taht if i DO have the heads off, might just bounce the cr a bit while im at it... this injection is very very safe and could tolerate another .7 or 1 point easy i figure.

Maybe I should add that I was referring to Edelbrock's marine heads, I have not checked all their variations of automotive heads.
The marine heads comes with s/s intake valves and inconel exhaust valves but without springs, retainers etc.