No, it's because my donor didn't have the right setup for using a evap system with a stock '85 gas tank.

I see from your write-up that your donor was a 2004 (3rd gen engine). Here's a summary of what I think I've learned so far:

1'gen  95-96  Distributor, EGR,     1 Cat,   1 EVAP Purge line,  1 EVAP vacuum line,  1 solenoid
2'gen  97-99  Dual  DIS,  EGR,      1 Cat,  ?  EVAP Purge line,  ? EVAP vacuum line,  ? solenoid
3'gen  00-04  Quad DIS,  no EGR, 2 Cats, 2  EVAP Purge lines, 4 EVAP vacuum lines, 2 solenoids, int fuse box eliminated easier/fewer circuits

Can you fill-in, add to and/or confirm any of this?