79 is the TRD size, 5K are 80.5. I am going to bore a spare block to see if the 80's will work but if I can get 79's I won't need to do that. It's in a KP61 Starlet & only for road & car club stuff so cast would be ok but forged is better.
I have managed to get all the TRD spec's for the 4k, port shapes, chamber volumes , cam profiles. Bob Holmwood has lent me them. His one made 140hp at 9200rpm in the late 70's. If I tame her down 110 would do me. Also have 35mm cv carbs of a Suzuki GSXR1100 set up for her. I got sick of the Dellortos & sold them.
What pistons do most people use in Aus?