jdm gauge install ????

I just got my 90-91 jdm gauges. Yeah, I know the dial from the tach and speedo won’t match up, the little tick marks, cuz mines a 92 but that will change in time. My question is should I swap the speedo from my current cluster to the jdm one or swap the tach from the jdm one to my current one? I think it would be easier to swap just the speedo cover, the part with the numbers and the needle cuz if do the tach I’ll have to do the whole tach, including the moving parts. Will this work?
Damn, I’m sorry if this is confusing. It must be friday. I can’t think of what the hell i’m writing.
L.