How Much Free Play In Drive Shaft

[Gregski]

Hi all, I tried doing a Search on this topic before posting I swear.

I have a two piece drive shaft with a center support bearing in my 2WD 1974 short bed with a Muncie SM465 4 spd. It appears that with the truck being stock and at stock height the drive shaft was already all the way in where it comes apart. As a matter of fact it was stuck solid and I had to use a puller/separator to get it apart. I don't know why? But at this point it doesn't matter. I have lowered the truck 2" in the front and 4 inches in the rear since then. And will need to have the drive shaft shortened so my question is:

How much free play should there be in the drive shaft? The manual don't say. So in other words with the car on the ground, wheels on the pavement, if I was to unbolt the rear U joint and slide the shaft in and out how much should it slide in and how much should it slide out?

Thank you all, be gentle I am learning about this stuff.