Don't run off. A couple of the guys here have gotten 460 headers recently. You're better off with headers that have long tubes, which promote low/midrange torque. That's what you need for a heavy load like a motorhome. The more popular, and less expensive, "shorty" headers are for HP at high rpm.
The Thorley Tri-Y headers, which come with a crossover pipe to a large single exhaust system, are the gold standard in Class C headers. Them and Bank$. Is your vehicle subject to emissions testing? It's possible that the emission system on the EFI engine calls for a different emissions complying system than the carbed engine does.
If God's Your Co-Pilot Move Over, jd
2003 Jayco Escapade 31A on 2002 Ford E450 V10 4R100 218" WB