Gents,
I was a frequent poster on the Gew88.com forum.
We had folks post about doing conversions to these. One thing to remember is that the pressure should be kept low, so I would go with a gentle round, nothing "elephant size".
I do believe they were small ring actions. Walther Lothar was listing barrels (in true 8mm) for around $200.00. Whereas Numrich had their "new"/ probably Chinese surplus barrels for a lot less. It is hard to justify buying a barrel, since they were generally sold for less than $60.00 without a bolt.
Generally the recent crop of Gew88's were pretty trashed. It is still common to find bare receivers for little money. Even the occasional stock pops up.
My criteria for "restoration" of these, is if there is a uniqe Serial Number/ year, or if it tickles my fancy.
I have also made a few of my own barrel shrouds. It does sound like this gentleman has everything needed to "restore" the rifle, if he so wishes.... but it would be an expensive restoration due to a missing barrel..... On less you have a pristine Gew88, generally they don't seem to bring much......
If I think about it... I might post my Gew88 early year Chrome model for you to look at!