S10 swap question about drive lines

[Sim6]

So I have an 87 s10 frame with a two piece driveshaft. I put in a sbc and turbo 350. I meassured my short shaft to be trimmed at 8 3/4". Driveline shop here said to meassure from the center of the yoke u-joint coming out of the trans back to the center of the holes that the carrier bearing bracket bolt to. With that they said before measuring pull the out 1" from being in all the way before I take the measurement. That's where I get my 8 3/4". Hope that makes sense they called me yesterday saying before they do any work they were afraid that a shaft that short would probably vibrate/ not balance properly being that short. He suggested a one piece shaft.

So my question is how short are some of your drive shafts? Any vibration?

The problem with going to the one piece is having to make/move a new crossmember that wouldn't be in the way of the driveshaft. Thanks in advance.
Jeff