Radiator options?

[Dave Kay]

'86 GMC Sierra 3500 (SW) 5.7(M) Q-Jet, w/auto and no A/C

Recently got this truck on the road and the temps are ok tooling around town but on the freeway it gets up there, like to half-way mark on gauge. Took it in to my radiator guy and he confirms that the radiator is way too small for this vehicle and needs to be replaced... I don't have an overheating problem, just higher than normal temps. Also, truck recently passed smog so it's not overly lean, carb-wise.

Radiator guy took some measurements and says he can build me one but without some kind of core with side-tanks it's going to cost extra. I'd like the biggest radiator I can fit in this truck that will match it's stock plumbing... it's going to be my big-toy tow vehicle.

My idea was to scour the local wreaking yards for something he can just re-core and save me some bucks, but haven't got a clue as to what model/year would be the biggest, sidetank-wise, then all radiator guy has to do is match them to a fat core.

Online search for new radiators shows about a half dozen different sizes for this truck (meaning core thickness) so we're both scratching out heads trying to figure out what model/year radiators will match-up with my truck's current plumbing and have the largest side-tanks/core potential. What are my options?

(do BB radiators fit an SB radiator front-support?)

BTW, I'm aware that radiator top-mounts and fan shroud may also need upgrading if I stuff something bigger in the hole, thanks.