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I have recently had a string of cooling system issues that started after I decided it would be a good idea to replace all the 20+ year old heater hoses and radiator hoses, flush the system with a garden hose, and then replace the thermostat while I was there.

I replace the hoses, thermo, and flush out all the old rusty coolant in the bottom of the radiator and it runs fine for a couple weeks, my water pump starts weeping so I swap it out

After swapping the water pump, I go for a test run and the engine overheats.. The water pump is pumping but it's getting stuck in the top of the radiator and not getting through fast enough.. A clog that shook loose I imagine. I get my buddy on the horn and he's got 2 radiators in his shop (JOY!):metal: a 3 core and a 4 core (AWESOME! an upgrade from the stock 2 core)

What do you know?!?! The 4 core slips right in, like a glove! (DOUBLE JOY!):metal::metal:

However, an unforseen issue has arisen... The radiator inlet and outlet are smaller than the inlet and outlet on my water pump/thermo housing. The radiator appears to be 1 1/4'' and the hoses for my water pump and thermo housing are 1 1/2"... The used radiator I am using is from a camaro's 454 that my buddy was going to use in is 455 skylark but he didn't end up using it.

This 4 core big block radiator should definitely work for my 250 I6, right? It dropped right in a matter of minutes, just the hoses are a different size? Do they make hoses that get taper? Can I just smear some high temp silicon sealant around the hose and tighten the hose clamps real tight? Do they make any sort of 'doughnut' or gasket that can fill this gap? Will there be any problems in the size variables?

Thank you all! I just wanna get my baby back on the road ASAP