Turn two into one, Tüv?

Moin I didn’t find a Tüvforum here so I just ask here for: An Omega A 26er with a very good body was bought, another Omega 3000 24v with good technology but bad body, what do you do? I would like the 26er to be used as a donor of a replacement / rough body and thus the 3000er to be preserved as such. In short, the 26 should be completely converted to 3000er and the FIN simply changed and the 3000er papers maintained. Ch to buy new raw collars as spare parts, actually the AKT of relabelling would have to be feasible after all? That saved the conversion because of other engine, other brakes etc.. What does that cost? Who does this, Tüvi or workshop master? ps: How to wrap numbers I know, but I want to have everything legal and an E (replacement car) in front of new FIN wouldn’t bother me Thank you, good evening to you! Gruss Willy