I've been searching this site (and others) trying to find an answer to my question but I haven't came across anything promising. Here it goes, I have a '67 with a 502 BBC and a Ron Davis radiator and I can't figure out what hoses to use. I really want to use hoses that are stock hoses (instead of the aftermarket formable stainless type). My set-up has a 1 5/8" dia upper at the engine and 1 1/2" dia upper at the radiator. I also have a 2" lower at the engine (water pump) and a 1 3/4" diameter at the radiator. Other than going to a local parts store (and getting a blank stare from the counter-worker) or buying 10 different hoses and using the trial and error method, anyone have a suggested starting point? I assume that I will need a 1 3/4" diameter upper hose (with an adapter) and a 2" diameter lower hose (with an adapter). If it helps describe my situation, I have an early model thermostat housing. Any help is appreciated.

Visit your local parts store and ask for the Gates catalog and view the hoses by size/length rather than application.

If I remember correctly, Gates does have molded hoses with one end larger diameter than the other end.

Early model thermostat housing = points directly to the front?
Another choice of housing style would be from a '88 newer truck, they point straight up, only if needed.

Good suggestion. I may browse for Gates online and see if I can find something. I was mistaken on the housing... I actually have a late model (66-75) that is pointed forward to the drivers side (see pic)

You can squeeze 1 1/2" over the T-stat housing, and 1 3/4" on the water pump. Those are standard sizes.

They might measure at 1 5/8 and 2" but the hoses will expand enough to fit.

Use WD-40 for a lube.

I just did a 502 and used those sizes.