Traction Problems/Time slip

[low&slow]

Got a 69 c10 long bed with everything stock except the engine. Truck has been gutted. The rear end is limited slip posi track. I took it to the test n tune this past weekend and could not get the truck to hook very well. My first few passes were on street tires leaving the light at 2200 rpms, spun the tires. One of my buds at the track let me borrow his slicks that are roughly 10 inches wide. Warmed them up and launched at 2200 again, but still spun the tires. Tried again launching at 1800 RPM's, did a lot better, but still spun before it decided to grab.

I'm sure I need to upgrade the drive train, but cash is REALLY low. What can I do to get the truck to hook better?

Also, my time slip info: (not sure if its good or bad)
R/T: .078
60': 1.972
1/8: 8.443
MPH: 83.02
1/4: 13.053
MPH: 100.56

The engine is a 500 Cadillac. Aluminum intake. 750 double pump holley. Headers. Stock heads that have been ported a little. Everything else is stock.
Dyno says the engine is 563 fpt and 477 hp. Not sure what its getting to the rear wheels though. The transmission is a 700R4 with a shift kit. For those that may question me, I have a BOP/Chevy Transmission Adapter Plate.