No real usable pressure carbs available for Lyc's, so FI is the only option.
390's have basically the same case as 360's so no change except cyl's are about 1/4" wider on each side, so baffles, exhaust, and plenum change. Governor is also on front of case. Motor mount is same.
As far as the prop, check the Hartzell prop info spreadsheet on VAF. If my memory holds, the later BA prop blade (7497) is recommended for the 390. I have the 7496 blade set on my 390 and thus have a yellow band from 2000 to 2300 rpm.
I really like my 390...
N299AD RV8 QB, IO-390X, BA prop...SOLD
N399AD RV12 almost ready for DAR
N99AD BD4, flew for 22 years...SOLD
N199AD One Design...SOLD
EAA Tech Counselor/Flight Advisor
CFII, MEI, CFIG