The problem is that there are no relay specs listed on the page. Only a list of components and the layout for the board. Without being able to look up the relay specs (because the part number is obsolete) I do not know how much current it needs to carry. As far as I know there are only two options, find a reference somewhere for the specs on the obsolete part, or calculate what is needed from the circuit. And I do not know how to do either of those.
Thanks you so much for looking into that. That information will help a ton. Because I have all the parts (even the relay you suggested), I think I will build it in the 'old' style with the relay for now. I look forward to trying it with a mosfet. I may wait until you work out the kinks! I will be sure to check back at your site in the future. Thanks again!