sounds like you have everything covered.

when I swapped the NV4500 in my 85 stepside I ran into header issue on driver side with the hedman 79080 2x truck header. #7 tube would not let me install ANY starter with the NV4500 hydro bell.

I used hedman 79170 for 72-93 4x4 or a 2x truck chassis.

another issue I fixed was the cross member needing moved back 2" for the 5 speed tail housing.

I trimmed the stock 727 auto mount then turned it around backwards keeping the cross member in the stock location.

I did trim the edge off the cross member to clear the tail housing. trimmed flat it gives about a 1/2 clearance.

if you move the cross member back 2" you will need to drill 8 holes to keep the side braces(which is a good idea for chassis stiffness/flexing)

fire wall hole is needed to mount clutch M/C- the 4 dimples for the M/C mounting bracket should be on the colum brace/mount but not drilled on a 76. , maybe? I know the 85 had the dimples not drilled but my 91-auto cab had them drilled with hole plug on FW.

I used a floor tunnel hump from a mid 80s ramcharger 4x4 to make a bolt in floor patch. it was auto 4x4 so I had to cut a hole for the shifter nad a patch for transfer shifter hole.

the granny 4 speed hole is not correct for the 5 speed shifter I had to do a lot of measurements on the 2 before cutting for the 5 speed.

I have all the pics if you want to see the couple tricks I used

heres the headers