Si me hubieras pedido...

Si me hubieras pedido...
 

I wanted to make a contrary-to-fact conditional saying:
Is this correct grammatically?

Yes, that's right. In Spanish the conditional corresponds with the past subjunctive. Be aware that you can also say yo pudiera hacerlo instead of of yo lo pudiera hacer.

It may sound better this way:
«Si me lo hubieras pedido ayer, podría haberlo hecho.»

I think that would be for a present contrary-to-fact whereas I wanted a past c.t.f.

Pudiera hacerlo and lo pudiera hacer are synonomous. The difference is a matter of the speaker's choice.

Yes, thank you, but what I mean is that for a past contrary-to-fact, I think it should be: