kloid,
If your run is really 145' one way, I would use a booster pump located nearer the spa. Otherwise you will be using 4" pipe!
Need to know how you plan to heat the spa? Are you using separate equipment? Is the pool pump and filter of adaquate size with the addition of a spa? Is the pool a similar distance from the equipment? Just things to think about.

Let me Clarify
I have an existing Gunite Pool and I am adding a new Spa to it.
The distance of pipe is about 145 feet away and I am using 8 jets at 10-12 GPM
I calculated the Head including fittings etc at about 61pounds of Head. By using some PVC engineering charts it looks like i need a 2.5inch return due to FPS velocity and a 2inch supply I would like comments. I am now looking at Pump curves and considering a 1.5HP Jandy Epump since my equipment controls are all jandy.

Comments and suggestions?

61 pounds of head or did you mean 61 feet of head?

Also, the 10-12 GPM/jet is that a manufacture recommendation and what size are the jet nozzles (1/4", 3/8" 7/16")?

Water velocity in the pipe is only one aspect of the pipe diameter choice. The other is the head loss in the pipe itself. For spas, you would like most of the head loss to occur in the jet itself for strong jets and an efficient setup.

With 8 jets and assuming they are 3/8" jets, I would target closer to 15 GPM/jet or you risk poor strength. Also, I would use 3" pipe minimum for that distance and number of jets. If you plan on going through the filter and heater, you might want to plumb in a pad bypass so that won't reduce the flow rate.

If do all of that, then the JEP 1.5 should be ok. I estimate an operating point of 115 GPM @ 56' of head or around 14 GPM/jet.

If you go through a filer and heater, the operating point could drop to 86 GPM @ 68' of head or 11 GPM/jet. However in this case, you have to make sure the filter can handle that flow rate.