I have the original radiator in my 53, meant for a 216, now with the 261 in it, it will spew coolant with a 4lb cap and 50/50 antifreeze after traveling a good while then idling for a prolonged time in 80+ temps. I might try a pusher fan, it will conceal nicely. Thinking it would be nice also to have it re-cored for a 4 cores too. Like to keep the stock tanks. But first I will install a puke tank to catch the coolant.

1953 Chevrolet 3100
261 cu inch, sm420, 3.55 rear, torque tube still,omaha orange, still 6 volt, RPO green glass, side carrier spare, all done
In the DITY Gallery
Video of the 261 running

1964 GMC 1000
305 Big Block V6, sm420, the next cab off restoration