After you crank the torsion bars up to level the front end, do you need to get a four wheel alignment done or will just aligning the front two wheels be good enough?

 

A 4 wheel alignment is for adjustable rear suspensions. You have leaf springs. If your thrust angle is off that much then you have something seriously bent in the rear.

Just ask your local ship for an alignment and tell/show them the vehicle. If they suggest a 4 wheel alignment, laugh and walk away. Below is Why:

Front-End, Thrust Angle and Four-Wheel Alignment
The different types of alignments offered today are front-end, thrust angle, and four-wheel. During a front-end alignment, only the front axle's angles are measured and adjusted. Front-end alignments are fine for some vehicles featuring a solid rear axle, but confirming that the front tires are positioned directly in front of the rear tires is also important.

On a solid rear axle vehicle, this requires a thrust angle alignment that allows the technician to confirm that all four wheels are "square" with each other. Thrust angle alignments also identify vehicles that would "dog track" going down the road with the rear end offset from the front. If the thrust angle isn't zero on many solid rear axle vehicles, a trip to a frame straightening shop is required to return the rear axle to its original location.

On all vehicles with four-wheel independent suspensions, or front-wheel drive vehicles with adjustable rear suspensions, the appropriate alignment is a four-wheel alignment. This procedure "squares" the vehicle like a thrust angle alignment, and also includes measuring and adjusting the rear axle angles as well as the front.

 

Also specify that you want camber set to zero or as close to zero as possible so that the tires stand straight up

 

Good info to know i will be getting the keys turned i think this spring.
how much normally is needed to lvl with back?

 

Until it is level and no more than 23.5" front fender lip to hub center.

This is a no brainer DIY, you just need 1-1/16" (27MM) socket, a long handled ratchet, and a measuring tape.