I think the issue with the A13 is that they are all the tall a14/a15 block height with either 76mm bores and 70mm stroke or 73mm bores and 77mm stroke?. This would mean they both use 133mm rods with either 36mm 76mm slugs (heavy) or 32mm 73mm slugs. The trick would be to use a 140mm rod in the 76mm bore one with a15 pistons with 1mm taken off the top or isuzu gemini or mazda slugs. That would make 2:1 rods stroke ratio suited to high rpm providing all else is right but for the street big bore A15 is nice.