stock shaft needs to be shortened to approx 50.5" ctr to ctr of ujoints , and then you need a ujoint that will work with the th400 yoke
reusing stock may get you rolling but stock isnt even 3" and with rust and age it should be upgraded when going t400 a good 3" or 3.5" steel shaft to 1350 yokes depending on your hp,rpm at traps and your weight
being cheap on a driveshaft can come back to bite you hard