[Dieselwrencher]

Jud, I'd install the intercooler now. It is a little more work but once you start driving this truck, you won't want to stop, and the intercooler swap won't get done. 2nd gen intercoolers fit this body style very well and are very affordable. You'll want one towing the way you want to.

You also asked if these frames were strong enough I think for towing heavy with the 6bt. I say yes, they are fine. My brother's 88 V30 DRW was together with a 6bt for years and abused more than most trucks and it was fine. The Yellow 89 2500 Burb I did has been on the road for a year and a half or more. Tony tows a tandem axle bumper pull dump trailer and he's said he's had 8-10k in it and his rig is on 35's. He towed enclosed trailers with it to St. Louis and Tn. He's put over 20k on it since the swap. I wouldn't worry about the frame as long as it is structually sound and hasn't had any hackery done to it. By the looks of the body on that truck, it is probably nicer than most of the old trucks in your area.