When you refueled were you completely out of fuel? Just asking because it happened to me once on my 12HT, that I ran it so low that when I refueled, I had crap in my tank and it pushed to the filter causing my filter to clog.
You could possibly have a vacumm issue with your solenoid, causing...
you could run two batteries just for the starter if you really want it and just buy the alternator. i got mine from 4wheel auto as well and yest it was super expeniisve
the 12volt starter is really nice i run the inerstate group 27 battery and it fires before you turn the key all the way.
from the research that i did and i could be wrong they were vacumm. if you cluster is round you will need the 62 dash pad. or you can swap out the gauges into your existing cluster.
just make sure you add the tube to lube 5th gear. anything else or questions you may need dont hestitate to ask i did the same conversion you are doing. good luck
Anest