maximum usable irs cv shaft angle?

Hello everyone. I have a quick question and just want to see if anyone has a good answer for me. Right now my truck has a thunderbird irs set up so it lays on the ground when the truck does. My truck had 29" OD tires on it but I'm setting it up for 31" OD and I'm worried about the cv shaft angles. I'd like to keep the cradle low to keep the third row but I'm rebuilding the suspension to have a low ride hight. Any information would be nice. Thanks guys.

It depends heavily on the width of the rear end. Im using a similar rear (mines from the Mark VIII) that I narrowed 6" to fit an s10 and it gets 10" of travel, limited by the CVs. Youll need to mock it up and test it to check travel.

From what Ive gathered, the Mark and Tbird IRS's are the same aside from the Marks having an aluminum differential, LCA's and a slot cut out (for weight or design??) in the UCA's.
Ive got a bagged Tbird with the stock IRS on 26" OD tires and the CV's bind when the car is fully layed out, so I couldnt drag it even if I wanted to or else i'd tear them apart. When I get home Ill be able to tell you how much travel the rear gets.

ok thats good information. i was planing on raising it 2" but might go with 3". are they binding cause the track width narrows to much? my truck was binding because they adjusted everything to get the most camber out of it to clear the wheels and when it was driven low it would narrow and bind because of that. Thanks a ton for your help.

i talked to Patrick the new owner of Matt long/kustom werks envoy and im not sure how much its narrowed (i think 2" each side) and his center section was about 2"-3" off the ground when layed out and it didnt bind when driven very close to the ground. That was on 29" OD tires. That is the reason why i posted this cause i was shocked how much travel it got even after being narrowed so much.

Mine binds simply because of how much its narrowed, I tossed all the stock arms and built my own with only 2

dave, do you have any pictures of your rear set up?