Ron Webb wrote...

Dry weight of an I0-360 is listed as 293#

Dry weight of an O-360, which is what the OP
referred to, is 30 lb less. I contend that
you'd have to work hard to get the FWF above
420 lb.

Do you *really* think accessories and oil
(in flight adjustable prop, not CS) make up
25% of a representative FWF weight?

Dave 'economics of scale' Hyde