Welcome Johan, we're happy to have you here.
I don't know if any of us will know the answer to your question so be sure to cast a wide net looking for answers.
As best I can tell the "Forward Control Chassis" is a GMC/Chevy "bread truck" that also sold as a cut down chassis for RVs.
I found a 1991 Service Manual for one. Perhaps this will help. If not... I apologize:
https://www.gmcmi.com/wp-content/upl...sis-Manual.pdf
I see references to a Chevy P30 in regards to this chassis. You might have more luck looking for info on that... IF... it's a valid description.
Ebay US seems to have a lot of Mid-90's Chevy P30 RV Shop Manuals for sale. You might try there:
https://www.ebay.com/itm/15093199835...tem23243f8697: