Ok, if you haven't already gotten rid of your ESC here's the link. http://www.73-87.com/7387garage/drivetrain/escrepl.htm And to bypass the EGR and EGR bleed solenoid. http://www.73-87.com/7387garage/drivetrain/lockup.htm This will work for 1986 and below, the 2 link is for 700R4 transmissions. Doing these two mods will remove:ESC and wiring through the firewall, EGR, EGR bleed solenoid and wiring, two TVS (thermal vacuum switches) and 99% of the hard/ rubber vacuum lines. This will basically restore your truck to pre emission.
Or just buy a C/K 30 or C6P C/K 20. No computer, no catalytic converters, no EGR from day one, emissions exempt.
ECS in (1983) 250 6 cylinder Do any of you know what year the ECS started? I'm replacing the (83) 250 with a (78) 305. On my 250, I only see (1) wire to the HEI, but still see the knock sensor with (3) wires by the starter on the 250. I'm positive the 78 version does not have the Knock sensor/ECS system, correct? When wiring the (78) 305, disconnect the spark Sensor? Is that all I need to worry about?
I believe 1981 was first year. Your 78 motor should have distributor with mechancal and vacuum advance mechanisms. Unless I'm forgetting something, these should be the only electrical connections to the 78 motor: Alternator Starter oil pressure sender temperature sender coil hot ground strap (maybe) battery pos. and neg. A/C (if you have it) block heater (if you have it) idle stop solenoid (if you have one) tachometer to distributor (if you have one) electric choke (not normally found on pre-85 models I believe your multi-pin connector to the distributor for spark advance was just for that and not the coil hot so it will be simply left disconnected.
I don't know the exact year the ESC was introduced but the enclosed wiring diagrams show your 83 as having it. If your going to eliminate the ECS then your 3/4 of the way there now. After it's removed you plug the pink ignition wire on the BAT terminal of the distributor. The knock sensor only has 1 wire going to it. It looks like a oil pressure switch. On V8's it by and infront of the starter. On the 305 just remove (if equiped) and plug the water jacket with 1/4" pipe plug.
