For AWD Aerostars you can never find a split joint boot for the front axles listed in catalogs. Then you go get a regular one and find you need to press the joint off to install it which makes that kind of useless.

You will need to remove your axle, remove the old boot (cut it off), and clean the joint of any grime with a rag (not brake cleaner!), then apply hi-temp blue wheel bearng grease or Ford CVJ grease. Then put the split boot on. I put red RTV along all the seams for a good seal on the boot and axle and used regular clamps on the shaft instead of the clamps included with the boot. There is enough room for a narrow slim clamp as long as the size is close to the axle size. Do not tighten the screws on the split boot too tight, it will rip/break. All you need is slightly finger tight on the screws and nuts. Kind of close the boot end to end so it can expand and contract with the axle and fold as the axle turns. Do not stretch it out all the way on the axle when installing it.

From Autozone:
Speedi-boot #03661

I think this is a listing for a GM truck. This was the closest match I could get with the old boot. I doubt most Autozones will let you do what I did, open the packages in an unattended part of the store behind the counter matching IDs of boots. I asked with a pretty please with sugar on top ;D