Hy. I have a A15 with an A14 H72 head(the oval port ,still not GX head, just oval) and the rest is stock engine. I got a 32/36 about 2 years ago and it runs excelent. I got it new, and for my engine model, and came with -Iddle jets:52 both.
-Main primary:140
_Main secondary: 165

In fact, for the smog/emissions test, I go down on the primary jet to 130(main), and 50 on the primary iddle, and I can tell the difference in the main jet performance, a little less pick up. The iddle, I can not tell, but the smog machine sure can, because without that change it is a "F" grade.
You say your A12 is modified, mine is not yet(A15 w/ A14 cyl head) so, make some adjustments.
The jets are cheap, about 3 dollars for the main primary(130) and 2 dollars for the iddle (50) I got for my webster,about the emulsion tubes, that I do not know to much except that , as far as many have told me, unless heavily modified or in a complete different engine, those should work within parameters, worry about the primary and secondary main jets(in the gasoline chamber) and the idle jets(one on top of the selenoid cut of switcth if you have one, or else, in the same place, but underneath a bolt instead of a cut off switch, easy access, buy several jets and try them on.
Jaime._____________________________________