dont worry about it...i fought my fuel system for 3 months before I finally got the ls1 up and running.
My 89 driveshaft slipped into my new 4l60e just like it did in stock 700 but I had to play with it a little. Twist and push etc...
1990 454 ss 2-4 drop, custom grill, rollpan....
1989 silverado: bagged, bodydropped, shaved, suicide doors, LS1/4l60e, 20" intro hammers/BFGs