D, have you seen this site? It looks like an analysis or discussion about A-series rods:
http://www1.ocn.ne.jp/~aori/driving/sunny_2.html

Dattoman:

Could you supply details re your Mazda piston setup in an A-15? Thanks very much.

Jack

I am using A14 block and head.
A15 crank and rods. Though A14 rods are the same.
ACL # 2699 UC Mazda pistons which start out dished. I have milled them flat as they stick a few mm out of the bore if you don't.
If you take a look at my carppy site you'll see a pic of the block with pistons assembled.
Mazda pins are 20mm so the small ends of the rods need to be enlarged.
Mazda pistons are 77mm std so 40 thou overbore required.

Its a beauty DD and it confirms what steve newing from speed tech said that you could use rb20 turbo pistons as cheap forgies with a little mod or the stock na ones for budget application.
But I wonder if 21mm is too much for the rods?