By chassis number do you mean the model? The Ford class A chassis is the F53, but the Chevy chassis designation is a bit more vague. They use both the P32 and P37 variants for a motorhome chassis. These numbers are taken from the vehicle VIN, positions 5-7. The P stands for "Forward Control chassis", the 3 for "One ton" and the 7 for "motorhome". Technically the P32 is the generic forward control chassis rather than motorhome specific, but some RV builders used the P32 rather than the P37 version. Not sure why - may be simply what Chevy did to fill the chassis order.
The Chevy Class A chassis is often referred to simply as "P30", to encompass the different VINs that may be in use.