I know a couple of people on here have rebuilt or plan to rebuild their own engines for their vehicles. I just wanted to make a suggestion for anyone who hadn't allready considered it: Gapless piston rings. In my 1987 CRX drag car, I saw 10-20% leakdown with standard rings. When I rebuilt my engine with forged pistons, I also installed Total Seal Gapless rings. The top ring and oil rings remain the same, but the second ring is actually two smaller rings on top of eachother with the gaps at opposite sides of the piston. After break-in, my leakdown was 1-2%!! I'll admit they were expensive (i think I paid $185 for the set), but if you could keep 8-19% more of the combustion pressure and by-products inside the cylinder, they should be able to pay for themselves shortly.
Just an idea for you guys to look into. I know if I build an engine for my del sol, I will definitely make the investment.
Since I don't have the funds to do it in reality, I like to built ultimate performance and ultimate fuel efficiency vehicles on paper. And believe me I've spent way over 100 hours, maybe even close to 1000 looking stuff up online and I've never ran into these before. It seems like a golden idea to me, especially for high compression NA engines and high boost turbo engines.