And... I think my 413 MH engine wouldn't care a whole lot. With 233HP @ 4000 it only needs 390CFM, and max torque is ~2000.
Maybe a little better flow-tune with 4-2-1 and small tubes?

One oddity I recently found was that the VIN plate doesn't match other published figures; VIN says 233@4000
Mopar chart says:
Dodge 1971/72 V8- 413-1 4 BBL 4.188 X 3.75 7.5 to 1 265 @ 4000 445 fp @ 2400 Sodium Ex. Valves
Dodge 1971/72 V8- 413-3 4 BBL 4.188 X 3.75 7.5 to 1 238 @ 3600 407 fp @ 2000 Sodium Ex. Valves

It has the huge heads and MH manifolds, so it is a -3, but what is the definitive value for factory power?
Eric Bannerman on the FB Travco group I think has straightened me out, and I do have a 413-1 after all (I rechecked the frame # while matches the VIN and block stamping.)
"in my experience the number on the tag is only found in a couple places in factory literature as each engine has both a net and a gross HP and other publications often list the gross instead of the net that is listed on the tag. Even the stickers on the engines listing the HP are normally the gross number.
The factory 1971 salesman book lists the 413-1 HP as
Net 233 @ 4000
Gross 265 @4000
The same book lists the 413-3 as:
Net 215 @ 3600
Gross 238 @ 3600

the salesman book is just a source for both the factory net and gross HP ratings. Those are the books a Salesman used to look up options and such. The same information might be in the factory service manual. The 413-1 is listed as an option for the M375 and that's the only 1971 application it was used in as far as I know. The motor homes used or were available with the 413-1 through 1973 when the 440 replaced it.
All the truck 413 engines in 1971 used the truck style parts like the exhaust manifolds and such instead of the car version of those parts. So what you have is probably the original engine."

The important #s to me are 445 fp @ 2400 if I'm going to re-gear the drive train.

I'm still not certain what the -1-2-3 models are; if the -1 is in motorhomes and the -3 is in D500s and the like, is the -2 the car model?