You will need to drop your crossmember using a spacer kit or install a SYE to avoid driveline vibrations even when you do get the front suspension in.
4 degree shims for your rear axle perches will help point the pinion up at the Tcase where it belongs and that will help quite a bit too, but the slip yoke being pulled out and at a poor angle for 1 Ujoint can only be corrected with a SYE and double cardan driveshaft.
Baseline outfiters sells a complete SYE kit for 150 on sale once in a while and usually around 170. IRO sells a HnT SYE for about 50 less.
A front driveshaft from any automatic XJ will be a good replacement for your rear DS when the SYE is installed.
'00 XJ - Somewhat modified
'01 Venture - high mileage, paid for, shut it