I have a post war Lionel 2333 F3 I've custom painted. I want to replace the original "growler" motors with a WBB re-power kit. WBB makes an F3 and an F7 re-power kit.

What are the differences between the two (other than the obvious that,  one is for F3's and the other for F7's)?

Which would work better in my application to the 2333?

Secondly, Are the side frames interchangeable between the two?

Any help would be appreciated. Thanks.

Mark