Can you keep the old small-block radiator for an LS swap, and which hoses fit with a Camaro water pump?

You can often keep it, and the pump choice matters here.

The pump: most LS pumps put the upper hose on the passenger side. The LS3/L99 Camaro pump is different: our water pump data (from ICT Billet) lists its outlet at the upper driver side — the same side as an old small-block's upper hose. It's also one of only two pumps that clear a VVT timing cover. Match it to your accessory drive spacing (-3) — see which water pump.

The hose size: the LS upper outlet is smaller than older engines'. Speedway: LS upper hose is 1-1/4 in (smaller than SBC/BBC). An adapter to the radiator's 1-1/2 in inlet solves 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.

Don't forget 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. Route it to the adapter's barb or to a radiator steam port.