I would like to convert from crossover with bypass to stock setup with circulating pump. Looking at the pumps it looks like there is a return fitting on the top that connects to the intake manifold. Engine is a 496 stroker with Merlin intake. The intake has no fitting to connect to the return on the pump. Can I just block off this return on the pump? Thanks.

Yes. Block it. The late model 4 port t-stat housing is the one to use. It allows water to still circulate when t-stat is closed. T stat sits on top of that 'spacers' pictured. Note: orientation of that t stat spacer very important as it directs water flow in the housing.

Thanks! So the t-stat spacer should have the opening facing the front?