RD 250 350 400 tachometers interchangeable?

[RDnuTZ]

I'm working on a couple RD gauge clusters and wondering if I can directly swap a spare 1977 RD400 tach into a 1974 RD350 gauge cluster? Quick visual comparison looks like it should fit mechanically. Is there any re-calibration or other fixes required to adapt for the swap? I have a box of misc Yamaha tachs from various models acquired over the years and wondering about functional compatibility between OEM tachs for 73-75 RD250 vs. 350 vs. 76-78 RD400?

[m in sc]

all yamaha and kawasaki mechanical tach use the same ratio

[RDnuTZ]

well that certainly makes life easier! Thanks Mark