I am needing some parts for 'big-bolt' (2.5 T 6400) COE...like fender treads, screw holders (clips) for floor board mounting. Who/or where to start looking for these plus I'm sure many others. Can someone tell me what engine I have year cu.in. etc.?? It is a GMC # 270827198. Also where to get wiring harness; plus por's & con's on converting from 6 volt to 12 volt. Thanks coe leo.