Need advice on a 4.5 in lift

I'm about to lift my XJ 4.5 inches. I know of some folks with a 4.5 that didn't need an SYE or shafts. When I lift mine what are the signs to look for that I would need an SYE etc. ?

By the way it's an 87 model

any vibes, plus you can check the pinion angles

most likley you will not need one with an older xj, make sure that you use a t case drop though, I did a 4.5 on my buddy's 89 and put on the tcase drop and he has no driveline vibes or death wable.

I did a lil over 5 inches in the back and right at 5 in the front.
I used the t case drop that came with my kit,and had NO vibes with an 89.
About 2 weeks ago i swapped out my stock springs, with 3 inch block and 1.5 shackle for a re 4.5 full leaf pack and the 1.5 shackle.I now have vibes from about 5 -25 mph.
im not gonna fool with it as i am planning to put my d44 in in a few weeks and i dont drive it much(2-3 time a week)If i have vibes then, i will go the SYE andTW shaft$$$$$$

Thanks for the advice guys !!!!!