The 944 trailing arms just require using the Type 1 bushing (torsion bar mount). Here's a pic to show that setup FWIW
If you've got a Ghia setup up front I've heard of a good brake bias with those paired with the NA 944 rears, I think that is when using the 944 master cylinder IIRC. Personally, I would worry about brake fade on the front with that setup, but it's not like you'd be tracking the car. Also, you would have to re-drill the fronts to be the same as the porsche 5x130mm rear BCD instead of the 4x130mm, unless you were ok running differing bolt patterns. Might be best to just get a rear disc kit somewhere.
The 944 axle flanges are also 100mm like the T3, so they are a nice upgrade too.
Are you upgrading the transaxle? 76-79 bus 6-rib is a very nice strong option.
One other question, how much POR-15 did it take to do the pan?