350 sbc timing question?

[cberry121]

Ok so here's the deal. I bought a new GM goodwrench 350 crate engine, also have a brand new rochester quadrajet, and new msd ready to run distributor and coil. To set timing I put my finger over the #1 cylinder spark plug hole as i cranked the engine until i felt compression. I then put it at TDC. Which means i was on compression stroke. Truck fired up decent, even idled at about 700 no problems. Give it any throttle at all and it backfires through the carb with mostly gas and the occasional 2 foot flame, and stalls out. I then tried resetting timing at 8 degrees BTDC. Same issue. Firing order is perfect, rotor on the dist points right at #1 cylinder like it should. I have no clue what else to do. Is there a carb issue? mismatched timing tab and balancer? or is my timing just that far off?