The MPFI intake will not bolt to your current EA82 in your subi - the heads are different in terms of the intake ports, so you'd need to swap the heads as well, in which case you might as well swap the entire motor if its in good nick.
I've got a wiring harness that you'd have to cut out of an L series touring wagon loom. The loom has been spliced under the rear seat, that's why I say cut it out (everything worked but there was a drain in the system somewhere that I couldn't be bothered chasing). I swapped the looms when I did the EJ conversion.
I must say that I found this site when I was doing the MPFI conversion to my subi a few years back. I was well into it and most I spoke to here said I should have gone for the EJ conversion from the start. I knew nothing about it at the time and stuck with the MPFI - which was a good upgrade IMHO (for what I wanted then). Since then I've gone through two of those motors due to a dud radiator, back to a really bad carbie motor and now to the EJ after a bit of work. I've basically done what you're looking at doing but with the EJ - powersteering, power windows etc. Best thing to do would be to start with an MPFI touring wagon and go from there - all the hard work is done for you
Cheers
Bennie