My ECM is a 1227747, there are a lot of PROM chips available for it (listed below), mine was a ARJU, a Calif. chip. I would like to know more about each to be better able to choose the best one for me.

ACSU, ACSW, AKAL, AKAJ, AKAR, AMUR, ANLW, ANLX, ANLZ, ARHT, ARJT, ARJU, ASDU, ASDW, ASDZ from http://www.exatorq.com/ludis_obd1/c3xref.html

I have a '90 Sierra 1500 2WD, 1/2Ton, 5.7L TBI, R700. There is no AIR pump on it but I cannot be sure if the engine originally had one. The truck was originally a V6 with a Manual tranny. The engine, tranny, & wiring was swapped from a California truck by a previous owner, However I live in Arizona.

I found the following info. at http://www.diy-efi.org/gmecm/ecm_info/1227747/, it is sort of what I want but I am sure that there is more important information than what is displayed below.

ABUL 1987 Astro with the 4.3 Z TBI,1227747
ACSU 0024 1987 V 1500 (Suburban) 5.7L, 700R4, 4x4, 3.73 axle ratio, and AC.
ACSW 87 C1500 pickup, 5.7L TBI w/T700R4,1227747
AFDY 6022 5.0 automatic
AJUK 88 C1500 pickup, 5.0L, Auto, 1227747
AKAJ 1147 1987 K 1500 5.7L, 700R4, 4x4, 3.73 axle ratio, leaded compatible (no closed loop) and AC.
AKAL 87 5.7L automatic
AKAR 1180 5.7L manual leaded fuel option (no closed loop)
AKDX 2088 4.3L automatic
AKSN 88 4.3L 5spd
AMUR 88 C/K pickup, TBI EFI system, 1227747
ANLW 5469 89 5.7L automatic
ANLZ 5483 5.7L automatic
ANTZ 89 7.4L manual
APAB 4.3L manual 3.42 rear end ratio
ARHT 7465 5.7L manual
ARPC 7509 5.0L manual
ASDU 1991 Chevy C-1500 5.7L V8 Auto
ASDW 9544 5.7L manual
ASDZ 9578 5.7L automatic
AZFT 9503 7.4L automatic (THM400)

I understand that I could program one, if I am ready to buy more equipment, but first I want to understand PROMs from the OEM standpoint.
Sincerely Jon