318>390 Stroker.......Your thoughts

I've read many threads in here and most shout 'go for a 360'. They are rare in the UK and if you find one very expensive to procure. So that's not an option for me. Guy I know paid £3000 just for a block, no heads etc.
Biggest issue is piston choices for the 318/390. Trying to get the comp ratio you want is very hard.

My options are 9.9:1 SCR or 11.5:1 with what I can find.
Shame as ideally I want mid 10s.

Always wanted to keep the 318 as a base, but wanted something to kick me in the back when I romp on it. Cubic inches was my choice to do both.

compression is important, no doubt. That said it certainly isn’t a deal breaker.
Going from 9.9 to 11.5 might be a 4-6% gain due to the extra squeeze. 500 horse motor that’s 20 or 30 horse, not nothing, for sure , but also far from a deal breaker
Could be made up other ways, certainly