I'm swapping a 3.4 into my 89 Pickup I order the dipstick guide for the t 100 and it didn't fit seemed to short to reach the hole. So I'm wondering if I can use the old dipstick and just mark it to where I need it.

 

You need the dipstick union, as outlined in this post:

https://www.yotatech.com/51750314-post2.html

It takes 4 pieces/parts to install the dipstick