have experience with a Shadow Cruiser TC, (1993) ?

I have the 1995 model of this camper. It will fit and should not interfere with the holding tanks/dump valve area. You may need to ensure adequate cab height clearance (2x4 boards would add height and cantilever support if tailgate is not used). Don't think the tailgate would be much cause for concern, though. Just make sure you have good tiedown support. My TC sticker indicates 1868 lb. fully loaded (40lb propane and 17gal fresh water).

The guy that bought my old Lance Squire hauled it off in just about the same set-up(pickup) with the tailgate down holding the rear but the Lance was like 8'6"..He uses it today as he did a couple years ago without issue.

My advice would be to get some tailgate supports..I have looked hard at them to haul my Yamaha Rhino in my 8 foot bed with the tailgate supporting some of the weight loading.There not to expensive like $60 or so.

https://www.dgmtailgatesupport.com/product-category/tailgate-support/

No experience but also check the truck cab height clearance.
As to the tailgate, its not designed as a load bearing 'bed extension'.
Really doesn't offer much resistance to weight. Weakest would be the cable mount points.
Only reason might work is I assume camper doesn't weigh that much.
But the camper itself may yield if not fully supported?

Yea, that was not safe, he didn't even have his talegate down!

Like this?

http://forums.trailerlife.com/index.cfm/fuseaction/thread/tid/29406953/gotomsg/29535361.cfm#29535361

In all seriousness... watch the rear axle weight.

I think the major question is not if you can make it fit, but how strong is your tailgate.
25 yo camper will likely have weak floor, so it might take some reinforcing all together.