I have a 89 GMC Suburban 1500 4x4, original 350, TBI, 700r4 tranny. I swapped out the engine putting in a 383 stroker, 1.7 Roller rockers, Edelbrock performer top end package and I believe a Jegs flame thrower distributor, and long tube headers. The truck has been sitting for four years now because I cannot get it to run. It'll start right up but cannot/will not hold timing, jumps from 20 bdc to 30 tdc. I need an O2 sensor but it needs to be about 6-8 inches longer than stock to account for the headers. Please help, I've got almost $10,000 invested between the engine and suspension and I've put 1200 miles on the suspension and 50 tops on the motor.