Have not read all 6 pages, but if it were me, I would over shoot the 13.5 goal so you have some room to play. If you want to do well at index racing, you need to be able to run faster than the index so you have room to adjust/play (depending on your driving style).
For example: I ran a 10.5 index a few times this summer, took out a lot of cars that could not quite run the number...cars running 10.55-10.65 were not competitive at all. Mine was capable of 10.3, but I could slow it easily to 10.5.
Anyway, long story longer...heads, GOOD converter, and street slicks would probably get you there, although if I went that far I would get a bigger cam, add headers and a Holley 650dp (Proform main body, no choke horn). All that would put you in the 12's, then you could slow it down into the 13.5.
If your J heads are ported, then I would just get a bigger cam, converter, headers, and 650dp.
Racing is not cheap, but there are many different ways to get you to your ET goal (some of those are cheap, like tuning what you've got).
