Slip yoke length

I have a 64 Falcon with a 289 and c4 tranny. I put in a 8.8 rear end needed a new drive shaft the one that was in there from the 9" was to long. I took an alminum one out of an explorer and with the yoke for the C4 on it and bolted in place the slip in 2 1/4" I know the optimel lenght in 1" . I can get a spacer for a mustang that in 11/16" and it will bring me closer to the 1", so after a long winded post how much slip in the yoke is to much?

 

Well, you lost me along the way, but I was taught to push the yoke in all the way, then pull out 5/8"-3/4" and measure center to center with yokes in rear end.

 

When i got my first one done that is what i did, but i was told 1" . I have 2 1/4" is that to much and what could happen if i drive it? I dont think it will fall out the splind area is almost 8" long.

 

Yes sir, this would be the correct way to go.

 

I had to make changes in my build after I had driveshaft built and the spaceback is 1&3/8". I'm going to try it and if it's got a vibration, you can guess what my first change will bw!
Dave