TKO 600 PROBLEMS

I have the trans in but when I installed the driveshaft, the driveshaft will not rotate. The car is in neutral. I no im not bottemed out because i can move the driveshaft forward into the trans more. Also Im not sure the trans shifts into 1st. Does it barly go into 1st? I have an aluminum driveshaft with the 31 spline slip yoke. The crossmember is modified, Mcleod bellhousing and have a new clutch disk. Does anyone have any ideas?

Thanks
Ryan 92 stang

I was able to shift through the gears with the trans out of the car, had the same problem with first tho. didn't look if the output was rotating, sounds like the trans is coming back out.