I don't like to second-guess distributors, but if they saw 120V AC modules and didn't quote a 1734-FPD, you need to review all the choices.
When building a POINT I/O system you can use the Rockwell product selection tools like Integrated Architecture Builder, or the manuals themselves. For POINT, you always need both to Selection Guide and the individual Installation Instructions (these have the wiring).
In general, POINT I/O modules use the 8-terminal 1734-TB terminal bases.
The 1734-TB3 terminal bases have 12 terminals, with several connected together (4-5-8-9 and 6-7-10-11) for more access to the Field Power Bus.
A quick look at the
1734 POINT I/O Selection Guide shows that the 1734-IA4 and the 1734-OW4 modules both require the ordinary 1734-TB terminal blocks.
A look at the 1734-IA4
Installation Instructions then shows that the top 4 terminals are for the four 120V AC inputs, while the bottom four terminals are connected to the L1 (hot) side of the field power bus.
I don't think you can use the 1734-TB3 twelve-terminal block with the 1734-IA4. I'm not sure what would happen if you did !
Is the "upgrade" you mentioned the same as the CompactLogix and IA4 + OW4 ?