If it's a '69 or earlier Harley wouldn't they look for the engine number as their would be no frame number on an original machine?
Not around here. They'll just check the neck and be done with it. And that's ONLY if it's an out of state bike. If it's an in-state bike, they don't even check the VIN. You just bring in the title and a transfer sheet, and walk out with plates.
The only thing that matters here, is that your neck matches your title, and that only matters if you're in trouble for something, or you're buying an out of state bike.
I've had a bike with a mismatched engine/frame. Even got the case/neck checked once when pulled over for speeding. The officer just said 'oh, blew up the original motor?' 'yep' 'Alright. Bike's not stolen, slow down and be safe'
This is BFE Texas, though.
I'm sure Cali is way different. I hear they can smoke weed, but can't have double edged knives or buy guns whenever they want. *shudder*