Compression ratio help please 327 (331)

[Beemerlite]

Hi one and all from the land far down under, New Zealand to be exact.

I’m looking for some info on a suitable compression ratio for my engine.
A little back ground on my engine and what I can remember about it!!
I had the engine built 27 yrs ago when I was in my early 20’s.
Ok here go’s, please again it’s what I can remember.

Small Block chev 327 (30 over 331 )
Casting # 3782870 unable to read the deck casting numbers as they have been machined off.
Heads double hump fuelie 461’s with lots of work done to the ports.
202 inlet 160 ex 3 angle valve grind, stainless steel.
Titanium retainers screw in studs.
Treble isky valve springs
Anti lube/pump hyd lifters.
Yella Terra roller rockers.
True roller timing.
Small journal 2 bolt mains steel crack shot peened and balanced.
Rods are standard chev, shot peened and balanced.
Pistons forged TRW 12.5 high domed with chrome moly rings.
Edelbrock Victor Jr intake.
Holley 750cfm 3310-2 carb.

I have no idea what the cam spec is as I lost the spec sheet. But when I had the trans rebuilt 25 odd years ago TH350, I had the torque converter done to match the cam. The torque converter has 2400RPM stamped on it.
Had one hell of a lumpy idle! and could pull very high RPM…

Now for the fun part… I haven’t used the engine for about 20yrs.
Probably only done 15000 miles on it way back then.
About 9 years ago I had the engine completely rebuild from the crank up.
It’s been sitting on my engine stand ever since.
The valve springs have not been torque down so there isn’t all the tension on them.
I turn it over once every two months or so and spray CRC down the bores.
I used the engine in my street car, then a 1975 Chevy Monza Spider, daily driver.
Took it out when I sold the car and placed a 305 back in it.

My Problem… I think…Compression ratio.
I would like to put this motor in my 1989 GMC C1500 at some stage. But I need to lower the compression ratio? So I can run it on todays pump gas. The GMC’s my daily driver.
What would be a suitable compression ratio and a good piston type, to run in my engine these days. We have 91, 95 and 98 octane fuel here in New Zealand at most petrol stations.
Since I’ve had the engine for over half my life I’m not selling it... lol
But would like to be able to use it in something… one day.
My truck has the stock 350 in it and runs sweet as, 246000miles on clock. Was rebuilt at some stage in the States before it was shipped over here.

Sorry for the long winded 1st post but thought a might as well throw it all out there...

I'm gona try and add a few pictures.

Thanks for any replys...