This stuff appears to be factory installed and is all over longitudinals and floors. I haven't seen it on any pics of folks floor repairs or chassis stiffening. Is it available aftermarket? I see many folks using Dynamat as a replacement instead.Click to view attachment

In all my 25 + years of taking cars apart I have NEVER seen tar material on the longs. Yes, it is available.

My factory 6 #269 has/had the sound deadening on the inner longitudinals

Caution, your perspective may be distorted, yes the car is sidewise and there is no floor pan, but you can see where the sound deadening was removed

I bought this. Should be enough for the whole interior at least once.

eBay Item 121069527339

Last time, I used Dynamat, and it was pretty expensive to do the whole thing. This time, I bought the generic version, and honestly, it's about the exact same. Just about 1/4 the price.

Good tip! I laughed when I saw where it is located. Hutto, TX. I own a house a few miles from there. Guess what their school mascot is?? The Hutto Hippo's. Seriously; some group of peep's thought that appropriate?

I went with Rattle Trap, a thicker version of Fat Mat as I wanted to keep the interior as quiet as possible. I think it was about $100, purchased off ebay with free shipping. IIRC, it arrived in a day or two.

+1 on Gmat

Thanks for the input. Have ordered some Evercoat 116 Q-pads and some G-mat to check out.
I have another question – on the passenger side, the center tunnel piece rests on top of the sound deadening padding and is not welded to the floor. Is this correct or the result of sloppy workmanship when the car was built? The center tunnel piece is welded to the floor on the driver’s side.

When the weather warms up, I'd like to dump some sound proofing into it, but was wondering if I need to remove that tar junk that they have on the floor, and if so, what would be a good way to remove it, or should I just go over the top of it? I think my firewall is already missing that rubber junk already.

I would think this would be enough to do the interior??

http://www.ebay.com/itm/Rattle-Trap-25-SqF...e25&vxp=mtr