Just forget about the lock-up,don't worry about it,yea you may lose a little in gas milage but from what it sounds like that isn't a concern.It's not like you need it or the trans wont work,it's for better fuel economy PERIOD!just unplug it.I've swapped a few trans in cars which didn't have provisions for lock-up,(we swapped for the overdrive)and never had a problem,EVER.Some may say that it will have to much slippage because it's not locking and may cause it to run to hot,Well i've yet to see it happen,and if that was a concern then put in a extra trans cooler,and you would NEVER be able to feel the differance.I couldn't tell if it was slipping,which i don't think it was.unplug it and forget it,don't let that be the reason you stick with the ECM.I would do the same your doing,trash the ECM use the holley or a non computer Q-JET and get a vac. advance dis. and your ready to roll.I've found the cars seem to run stronger without a ECM trying to retard the timming or lean or richen the fuel control just when you trying to race someone,it will never fail the car will fall flat on it's face.A buddy of mine did this to his monte ss.The car ran like 16.8 stock with the stock ECM,carb dis.He messed with it endlessly trying to make it faster,but couldn't do much that the ECM wouldn't try and correct,so he took off the carb got a stock non computer Q-JET ,put in a vac.advance dist.(which by the way you can tailer the advance yourself with differn't springs)and a set of headers with dauls,the car would now run 14.8 sometimes even better,Dropped two sec.and never even opened the motor,did i mention it had over 100,000 miles onit.And he never had a prob.with not haveing the lock-up not working.so ECM or not,I think the results speak for themself.