What radiator should I use for an LS swap in a C3 — budget vs direct-fit?

Direct-fit: companies like Afco, DeWitts and Frostbite make LS swap radiators for a wide range of vehicles. They drop in like a stock part, with the upper and lower outlets and steam port where the LS needs them, and you can often choose the finish and a single or dual fan shroud. Speedway's view is that the convenience is worth the price if the budget allows.

Budget: keep a conventional radiator and adapt it. Speedway's LS swap radiator hose adapter (listed at $24.99 in its article) fixes both problems at once: a 1/4 in hose barb takes the steam line, and it adapts the LS water pump's 1-1/4 in upper outlet to the 1-1/2 in inlet on a typical radiator. Or use a universal double-pass radiator, which puts the upper outlet on the correct side and can cool better than a single-pass. Expect some modification to fit a universal radiator in the car.

Either way, plumb the steam line — On most LS engines the thermostat sits low, on the water pump, instead of up top like older small- and big-blocks. GM added steam lines in the cylinder heads to vent trapped air and keep hot spots from forming at the top of the engine.

We haven't verified a specific C3 Corvette direct-fit part yet, so check the maker's application list for your year.