How will I know if the drive shaft is too long?

[JGross]

I'm getting ready to do my 5.3 swap, I'll be replacing a SB 350 / TH400 with a 5.3L /4L60E. I know the new setup is longer than the old one so I've moved the 5.3 foreward some but it's still about 1/2 inch longer. How will I know if the drive shaft is too long? If I can get it installed into the U joint at the differental is it ok or can it still be too long and cause damage to the trans as the rearend travels up and down.

Thanks
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