[gainsy]

Looks like it either started life as an xl & had a procat rear end added or it was a procat that they used the chassis from an xl to save weight, you can tell it is an xl top deck from the front of it as it curves out like the swb one did, the xls ones were straight as was the procat one, looks like you have the procat layshaft fitted so you more than likely have the rear diff as well unless there is an mms one hiding in there
Get it stripped & cleaned up & a new procat chassis set can be bought from Fibrelyte or Factory Works, new bodyshell sets are available from Penguin RC on ebay & fit great