Gears & Axles - how strong is the 1998 steel driveshaft

I have an m6 with a ford 9" and ET streets.
Using the stock aluminum ls1 driveshaft right now but worried it could twist.
I have a 98 steel driveshaft.
Instead of spending $300 on an aftermarket driveshaft I was thinking of just putting a Spicer 5-795x u-joint and napa 447 u-joint in.
Other then a little more rotational weight, would this be decent stength upgrade for almost no money?
Seems everyone goes aftermarket DS. Is that because people don't think about the 98 steel shaft or just that they wouldn't be a good alternative?

Bad idea.

While it may not break, the stock steel driveshafts are
not stiff enough and are prone to whip if overspun.
This is how a lot of people break tailhousings. Any
gear ratio higher than the 2.73 wants the aluminum
or aftermarket.

Plus, the stocker really isn't the correct size for a 9". For your own and others safety, get the right DS.

Do it right. I got a 3" Steel from Denny and working fine.

I've seen M6s lift tire on a stock steel DS. While I believe they are stronger and less prone for failure on launch then a stock aluminum shaft, I can't give you the advice to do this. I would recommend getting a good shaft.

I've also seen a local guy bust both the trans and diff
yoke with the steel driveshaft, which came out looking
OK.

It's not failure strength per se, but the inadequate
stiffness letting the shaft bow out (whip) at higher RPM.