You have a propane ,cushion tire, 3-5000 lb ,single speed forward/reverse.
With a sideshifter , I believe manu in1978, three stage mast with about 186-192" lift mast, forks look like 1.5x4x42" The exact capacity is on the name plate after the GLC ( GLC030, GLC040 or GLC050.
You will need a load backrest behind the forks to comply with the OSHA requirement $200-300.
The Mazda engines were very reliable- good luck with it.