Steve, I have about the same setup as you have. First make sure your radiator is in good condition and clean. The old guy that worked on my radiator also put on a new filler neck so I could use a pressure cap and plugged the overflow on the top of the radiator. (The new filler neck has an over flow built in.) It's just like a modern radiator.

If you do this it's important NOT to use more than a 7 lb cap. Any more than that and you will tear out the seams of the ratiator.

With this setup the only time my temp guage goes up is when I'm sitting in one place for a long time. I have toyed with the idea of adding a cooling fan on the front of the rad. just for the times when I'm sittin around, but I haven't done it yet.

Try out your system as-is in the warm weather and see how it performs. It will probably be ok.

George