engine swap 86 to 91

[5.0 novice]

First off I'll ask you to be kind, I'm new at this: forums and Mustangs.
I have a 91LX 2.3 with a fairly good body, no rust, and just aquired an 86 GT with a recently rebuilt trans but a rusted out body. I plan on pulling the 5.0 out of the 86, rebuilding it and dropping it in the 91. Although I'll probably have a million questions my first two are:
1. Should I keep the Speed density system currently on the 86 motor or change it over to Mass air flow which the 2.3 liter in the 91 has?
2. When switching the engines do I need to change the EEC since the 86 is first gen and the 91 is second gen?