MRL Mild 440

i've read that the newer FBO box is just a fancy box with a HEI module inside it. never had one apart so i don't know how true that is.

Yup. Nothing wrong with that, have run Dons stuff in the past on two cars and it's never let me down! And if you just wanna plug and play it's the ticket. But for less $ and less wires and simple clean HEI conversion, Greg (Trailbeast) kit from classichei.com is cheaper and just at as effective