For sure it can be done , a flex extension will help , I fought trying to install the bolts into the defroster vents for 3 hours one time , my customers girlfriend came home & just reached her small hands right down there & started them after I couldn't get it done !
Thanks guys. I posted this question when I got my new harness and was planning to get after it, but I broke my foot and had a 6 month recovery. Now the '68 is occupying the bay at the shop waiting for her transmission rebuild, so the '74 will wait...