Best EFI Choice? (GM, EECIV, Mopar)

[Jack E. James]

Group,
I am just starting out to convert some older motors (Ford 302, 460 for
now, but have 454 Chev and 390 AMC planned later, all in various states
of street/strip tune) and am looking for choosing a system to
"standardize"  my investment of hardware, software and "education".
Would anyone offer pros and cons for the major systems in wrecking yard
availability.
Is there any internet sources that consider the merits of one system
over another for a hot rodder?  Some items I believe important in
choosing are (order may vary):  1. loop processing speeds, 2.
"tunability" (should include backyard build it yourself kits or modules
for processors), 3. Software decoding, the understanding of control
locations for many years of availability. 4. Costs of external tuning,
software and adapters for making processor modifications.
Any suggestions welcome,
Jay