The wind is whistling in my cab.

I bought EXTREME for Shorty. I used extreme in our 1940 Ford build. The Ford build can be seen in Non IHC on this forum. I bought 8 rolls of Extreme and it takes what it takes. Any extra goes to the next project.
You should know by now, this is not a hobby for cheap persons. Your 4bta must have cost a few bucks. I do understand, I don't like dumping cash without some due diligence.
I have been buying my B quiet insulation from a local hotrod shop. I paid the same dollars in Canadian funds.
I am thinking that all of this automotive peal and stick insulation is expensive, B quiet has the best price.
Make sure that you do all the surfaces. Small gaps of under a half inch is probably OK. I used a rubber roller to make sure the insulation was well stuck. The surfaces MUST BE VERY CLEAN and dry.
Do you have a You Tube video?

Ok I was thinking extreme, because it's thicker. How quiet is shorty? I know this truck building isn't cheap, I'm just trying make sure I don't spend more what it's worth. I do have a video on my channel. I think it's called the Cummins swap is finished. That video it had no sound deadening except for the floor mat.

https://www.youtube.com/channel/UCmJJ3I ... subscriber

Shorty is very quiet. In fact one might say it is completely silent because the parts are in storage. The build stooped when our 1940 Ford came home from the restoration shop. The 1940 is quiet enough to almost totally deaden the sound of the stereo when the windows are up and doors closed. When I sit in the '40 the outside world seems far away, it so quiet, inside. I hope to restart the '40 Ford this weekend now the I have built a new "distributor" for the ECU.
Old IHC pickups are like drums and the cabs seem to amplify sound. My 1953 R120 had a 6.9 Diesel engine, those idi engines are loud. The cabin was quiet. I used a similar peal and stick sound and heat barrier topped by carpet with backing.

Did you just apply one layer I take it? I think I'm going to get one roll to do the firewall(that's where most of the wind is coming from) to see how well it works. Then order more. I also saw someone put a very dense foam on top the adhesive deadening on the firewall and back of the cab I might give that a shot. Also does your 6.9 swap r120 have power windows?!?!

I do not own the R120 with the 6.9 Diesel now. I gave it away. Yes. the R120 had power windows, electric wipers, Vintage Air and lots of other good stuff. I made custom brackets to hold Ford power window motors on the IHC window regulator gears. The gear pitch is the same. For wiring, I used the modular wiring from a Fox-Body Mustang for plug and play instant gratification. Older Ford window switches plug into the Fox harness. The Ford switches are easy to mount/adapt to the door panels.
Grounding the doors and NOT relying on an ground connection through the hinges, is important unless you are OK with slow windows.
I drove that "R" for 20+ years and 225,000 miles. With the Gear Vendors overdrive and the 6.9 litre Diesel/C6 automatic, the top speed was close to 90 mph or 145 KMH.
I did form fit closed cell foam to the firewall, on top of the B-Quiet. The automotive carpet with underlay made the truck quiet.
Do all of the surfaces. This is important.