TH-400 transmission question

[ers13]

Hi, I'm new to this board and have a few questions. First, I am in the process of re-powering my 72 Blazer with a new "Z" series crate motor with a new TH400. I was wondering if anyone out there knows the length of the output shaft required. I talked to the guys at Monster motor sports, and they said there were 2 different lengths. Second question, anyone out there in the North East have a good double wall top for sale including the hatch? My double wall is sagging on top and the hatch is trashed.

Thanks in advance!