I'm finally back at it and feel bad after looking at this thread, it's been years...

Before leaving off last I had bent the heater core tubes with a box end wrench but wasn't happy with it:



I never was happy with the way it looked, clearances, etc so went scrounging the junk yards and came up with what appeared to be the perfect core from a 94 Rodeo:



Unfortunately the new core is about 1/2" longer than the old original. I had to modify the 'left'(in this picture) hand side of the box so the core can stick through:





And these last two are from the trial fit. The heater core *JUST* barely clears the AC box inside the vehicle. I think I'd be doing good to get a couple of pieces of paper between them. But I'm happy to say it does fit and puts the nipples pretty much parallel to the firewall.