new here hello all

hello all , looking forward to learning as much as I can here I just purchased my second buick , an hopefully saved it from further neglect . I had seen this one at a few shows an it was for sale . luck had it now its mine , after looking it over there has been changes by previous owners that are going to be too much to bring it back to oem standards but overall still a good solid car an still has the 322 nail head . I decided to finish the resto mod . well heres a pic . I have currently begun the install of the leather power seats that came with the car at purchase , an upgraded the brakes to disc an drum . but whats totally beyond me is I cannot seem to find any info on the correct heater plumbing an why exactly is there hoses that run to what seems to be an external core on the bottom of the powerglide transmission ?

Welcome to the forum! Great looking 55 Buick. The plumbing to the transmission is a transmission fluid cooler. I've seen them plumbed in a couple different ways, someone else will have to chime in on the proper routing. The way I've seen set up is from engine, heater valve, heater core, transmission, to radiator. I always thought this was an odd setup because on a hot day, you would turn the heater valve off, stopping the flow of water to the transmission.
What are you doing for a booster and master cylinder with the new disc brakes?

Jacob , that's a bigger clue for proper heater line routing than I had ! thank you sir . now . the brakes you asked about , I bought the scarebird disc brake adaptor kit , trust me you cant go wrong with this kit you get the disc brake mounts a spindle adaptor , then purchase everything else off the shelf at your local parts store , via a very good supplied parts list . their kit is for using the existing single resivoir . these are the changes I made from here out . I did not add power brakes the brakes are still manual , I recommend using a 70's cast iron gm master cylinder from either a 1 ton truck or any of the full size cars . I used a early 70's buick master cylinder from a car that had NO power brakes . first you will need to cut a larger opening in your floor , then prefit the new master cyl onto the oem mount , it fits just place it as low as you can get it the factory opening an drill 2 3/8's holes an bolt it up . now you will need to remove the original fork from the old master cyl , an make a new pushrod assembly approximately 1 1/4 inches longer (you will trim this to fit ) using at least grade 10 allthread in the matching diameter an thread pitch of the fork you will need to make a carrier to install as the new rod is no longer attached to the master cylinder it will become a coned fit without the carrier the chance is slim but still there that the rod could come out of the receiving cup in the master cylinder this single part is the most important . ( check my pics )
order a brake proportioning valve from summit racing make sure its the one with 2 inlets an 3 outlets for disc drum conversions . install all nessicary brake lines an bleed the system .

Hose routing is here: https://www.teambuick.com/reference/heater_hoses.php

The way I've seen set up is from engine, heater valve, heater core, transmission, to radiator. I always thought this was an odd setup because on a hot day, you would turn the heater valve off, stopping the flow of water to the transmission.

yeah, that's definitely fubar.

the only way that could make any sense would be if the heater valve was a T that turned the trans cooler off when you turned the heater core on.

more sensible would be the circuit that shows to two parallel legs split at a T. the trans cooler always on.