CB350F CB400F oil filter compatability, exhaust studs

I've got a CB400F engine all set in a CB350F frame. Looks great, ready to wire, a few other details. One that's bugging me is this: the oil filter cover from the CB350F engine that I took out is clean, no broken fins, etc. The one from the CB400F engine is not. I thought it'd be an easy swap, and it looks that way. There is, however, a slight difference: the CB350F filter cover is longer, and the bolt uses a spacer. I discovered this as the CB350F bolt I have is torn up and the CB400F one was way shorter. I'm guessing there won't be any compatability issues -- don't seem to be any problems with it fitting on nor with it rubbing the front wheel or anything (the frame and front wheel are CB350F). Anyone know if there are any issues, or perhaps they look compatible but I'll be rewarded with a gushing oil spout when I actually get the thing running? Any ideas as to why they're different (other than the folks at Honda realized they could shorten it and remove the spacer, or perhaps the shorter filter looks better with the CB400F exhaust set up)?

Also: still need a few exhaust studs. Found them online for $2.50 each through a dealer, but after ordering I got the call that they were backordered with no foreseeable delivery date. Found new ones for about $6 each, but that's a big difference. Everything is new or has been repainted, so new studs would be nice...

Thanks all.