BLUEMEANIE - Its only been a few minutes (4 years - lol) since last seeing you in the forums.
Welcome back!
52Carl has a good suggestion on a radiator, but I would add a note that your later 261 has the low mount water pump which is gong to put the fan low on the radiator in your '51 and not pulling air through where its most needed to provide optimum cooling. You also may have an interference problem between the fan and crank damper and belt pulley due to the low location of the pump.
I would suggest you purchase and install one of Bolter
Pre '68 Dave's water pump relocation adapters to get your water pump up to the sweet spot on your radiator and you can enjoy trouble free cooling. Look up his moniker in the member list and you can reach out to him via PM.
Unfortunately this will require disturbing your very nice looking engine package, but I think its important enough to mention to prevent possible lack of cooling or overheating issues when you get your engine installed.
