Which heads are best

The smaller cam will run the brakes, but won't work because of the pistons. The larger cam will work with the pistons, but won't run the power brakes.
I agree with Yellow about D. Hughes and his opinions.
None of this is hyperbole unless everything is hypothetical. We have real specs for the lower end and the OP's goals. Unfortunately those "givens" now dictate the top end to work within the provided parameters. You need to lower static, giving up any chance of quench in order to be able to run a cam small enough to run power brakes and run on available pump fuel. IMO - the "right way" would be replacing the pistons with dished, rebalancing, and running a modern, closed chamber, aluminum head. I steer clear of Magnum based stuff because the valve train costs are higher and the return on investment over an LA-based head marginal (by my opinion).
If you don't want to redo the lower end, either run a stock head (the chambers will be larger than 74cc as cast...) and a thicker gasket to end up around 9.8:1 static, or run the open chamber RPM which are no different than the closed chamber except for the .100" deep chamber milled out of them. There is no power difference you will notice between the two models of LA based RPM.