[Roadsters] Radiator cap question

[Michael Knorr]

Can someone tell me what type of radiator cap a (low windshield) 1600 uses? 
Such as how many lbs. of pressure, suggested brand of cap, etc. My old cap 
has finally given up the ghost. I don't mean the "push-button" cap on the 
overflow canister, but the cap that sits just in front of the cylinder head. 
Thanks!

Regards, Michael Knorr
1966 SPL311-03639