What do I need for a proper under-dash rewire?

I seriously thought about coming from behind and putting them in backwards?
I did pull the windshield for another reason but also put a cut dash for my custom instrument panel in it ( all of the original dash hanging on the wall ). So I did install those 5 bolts from bottom up. The U nuts weren't much taller than the bolt head and the bolts weren't too long. Simply flipping the OEM hardware on my 67 might not apply to all models. If nothing interferes with the gasket lay....