Need help with numbers...

[48lesco]

I'm looking for some newer gears before I button up a CB77 transmission. Rounded dogs, worn grooves, ets. The engine is a CB77E-108333. There's a "gently used" transmission on ebay from a CB72 so I asked the guy what engine it came from. He replied CB72E-151291. Looks like a '61 and from the cmsnl website, most of the gears won't work for me. Just wanted someone with more knowledge of CB72's to verify. I know the spline on the output sprocket shaft changed, but did the gear splines change too? Silver book not as clear as it could be on this. Any insights would really be appreciated!!!