Fuel filler neck year differences

[obijuank5]

What am I missing to put the 79-83 two bolt filler neck on my 91 with the plastic shroud thing?
I want to use these because they are diesel filler necks. Had a tough enough time finding these.
Thanks

 

[sweetk30]

let me check i have parted a few mid 80's diesels and mite have some fillers for the 3 bolt plastic style i am not using .

 

[sweetk30]

o.k. here ya go . 3 box side filler hole pics showing why 1 fits and the other dont .

and i have 2 old style fillers with shinny caps like you posted from a 2 tank truck . and a c&c driver side tank truck i think with re-drilling the 3 holes in the plastic as there clocked 180* off will work for you and has a plastic fuel cap on it .

pic #2= 87 box for plastic ring hold in .
pic #1-3 = older early 80's and box side inner panel is not cut out as much and lets you bolt them up in place .

 

[obijuank5]

Thanks! That looks totally workable as is. I can just make a hanger type deal for the older filler necks and just fasten it to the newer upper section.
At least I should be able to.

 

[mrk5]

All I know is the style on the 73 always overflows at the gas station and I get a nice splash of gas on the ground. I try to listen for the sound of it getting full, but if traffic noise is bad I'll miss it.