Questions on 60 GMC 1/2T Disc Brake Conversions

[Legend56BC]

Hello All,My daughter is getting to the time were she needs to get a front only disc brake kit complete with the booster,master cylinder,porp valve etc for a "non dropped"6 stud.We have a hydraulic clutch in the truck before and has left 2 holes in the firewall,before we plug the wrong hole what hole was the correct hole to leave open?I think it should be the one the plunger rod went through just double checking. What company's are good and not so good.Is there any places that will discount pricing for members here?Any good bad experences with these kits we should know of with a tortion bar truck?Thanks in advance.Will post a pic of the double hole on the firewall.