Great Dane trailer questions???

Measure the length of the old, any shock will work as long as it is the same length. Truck off is fine, you will just need to push the shock together to align the bolt holes. Shocks simply dampers the oscillation from the road. They don't support the vehicle so not hard to collapse by hand

 

If you plan on changing them yourself, you’re going to need to have a lot of persistence and patience, as those nuts and bolts have been on there for 21 years.

You’re going to need a impact gun rated for at least 1400-1600 ft lbs of breakaway torque, a 1 1/8” combination wrench and a 1 1/8” impact socket.

If you have access to a torch, you can heat the bolts till they’re cherry red and then use the impact on it.

I changed all four shocks myself on a 2007 Hendrickson suspension, and in-between working and trying to take them off, it took a few weeks, but I did it without using a torch.

 

Have you tried contacting Great Dane and giving them the last 8 of you VIN#?