Check out your local Pep Boy's, look for Rhino Ramps. They are a polyurethane material and seem to be very strong. I have no qualms about puting the 560 on them, nor the Suburban. They have a wide ramp surface which should fit the 235's.
I think they set me back about $20.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.