[Healeys] Piston question

[Herbert Miller]

I am disassembling the engine for my BT7 (29E-RU-H/1355). The pistons have 4
rings, as illustrated in the parts manual, 3 compression and one solid oil
control ring. I have owned this car since 1970 and have on reason to believe
it has ever been rebuilt. Except for forged pistons with 3 rings, the only
pistons I can find have 5 rings, one below the wrist pin. My questions are:

When did they change to 5 ring pistons?

Are 4 ring pistons still available?

I know, "just buy 5 ring pistons and remove the 5 th ring" This does not
seem to be the right solution.

 

Thank

Herb Miller

1962 BT7