Dan said: "So what do you think, would a William's F7 B unit look ok behind an Atlas F3 A unit?"
I think it looks OK for the price from a distance!
Here are some photos for comparison;
Is it a new or old Atlas unit??
CP engines are new Sunset 3rd rail pricey, A is one with a steam generator so a bit longer then the other A units.
Silver are older Lionel with TMCC odyssey etc.
Black bodies are the P&D body kits can do them with any level of detail to match different versions.
The blue VIA engines still have to add stripes to the B unit.
The VIA Blue B body is the Williams B unit available for $89 at Trainworld and other places for a dummy also can be powered easily.
The VIA A unit is the old old old Atlas 2 rail engines. I have it wired into the Williams B unit that I powered and connected to the reverse board. This set I run with 8 MTH passenger cars, the 2 engines seem to work OK together with the front engine running with 2 rail scale wheels as long as I stay away from lots of turnouts.
The Williams B body does not look all that bad, ride height is a bit high price is right!
Let me know if you want any more detailed pics of any of them.
Click on any photos for it to open larger with more detail.