HEI parts interchange?

[Loki]

Im in the middle of the HEI swap on my 250cid. I picked up the entire set-up from a 76 c-10. Its the style w/ the coil mounted off the cap. not sure where the coil should be mounted.... I also have the cap and coil for a later model that mount together. I know the cap will mount to the distributor but i know the towers have a diff. location... Anyone know if the rotors are interchangeable or am i better off mounting the coil to the inner fender and putting the "combo mount" stuff on the shelf?

my camera is in Colorado at the moment or i would put pics up to clear any confusion about the Distributor caps in question.