please help! does anyone know what the font on the shirt is? thanks!!

Slim Dandy  Suggeriti da donshottype 
Thunder Mountain WF  Suggeriti da donshottype 

A clean version of a 19th century woodtype.
Walden Font sells a distressed version as Thunder Mountain.
Character set at https://www.waldenfont.com/typecase.asp?fontid=94
Still looking for the clean version.

The T-shirt lettering is a fair match for Slim Dandy, shown in Lettergraphics’ 1968 catalog as Slim Dandy (solid), Jim Dandy (contoured), and Dandy Outline, and in Formatt’s 1974 catalog as Klondike, in solid and contoured styles. No lowercase.
AFAIK no digital version.
Similar to Mansard (No. 121) a wood type released by Wm. H. Page in 1878. Fonts In Use has a page full of info on similar fonts: https://fontsinuse.com/typefaces/46218/mansard-no-121

This one was bugging me. There are such fonts that you feel you've seen thousand of time and yet you can't find them in the usual places. Kinda like this one.

Also hard to believe no one has made the digital version yet.

This would have fit right in with Michael Hagemann's Font Mesa.