1990 Q45 high side refrigerant fitting size / adapter?

[Q451990]

So at some point I'm going to replace the evaporator on the Q. I have R-12 on hand, so there won't be a conversion. I was looking, and the hoses for my manifold fit the low side port, but the high side port is smaller. I think I need a 3/16" - 1/4" flare adapter like this - can anyone confirm?

[Ryantzer]

I'm not sure I understand - I thought R12 fittings were standardized, like R134 fittings are?

[Q451990]

I would think so too, but mine has a smaller fitting for the high side than the low side. My gauges all have the same size fittings for both high and low. From my research GM and some other manufacturers did this.