I am consdering having my frame rails connected by having the shop weld on extensions. They highly recommend this for strengthing the undercarriage.

Has anyone done this or have any comments about it?

I realize that this take a bit away from the "originality" of the car - but I am long past this with all the upgrading I'm doing.. However, I would never do anything to alter the character of the car - I just want it to dirve better/tighter.

 

Do a search on subframe connectors. Tons of people have done it.

 

Yeah, it's a common way to stiffen up the undercarriage. Not only connects the front to rear rail, but you can also get one which connects the left to the right side of the car.

 

I'm getting these:

TCP SubFrame System

 

Are there any negative to reinforcing the Subframe. Is it possible the car rides too stiff?

 

adds weight? I only know a few who have them but have never heard anyone with any complaints... when the time comes I will be buying some for my 67

 

When you add weight, jut add more horsepower if you are into racing.

 

I'm leaving my 2.79 gears in the rear end so i wont be racing anybody... maybe a saturn or something.... lol

people were talking about the weight of a battery a month ago or something so i would say this would be talked about by the same weight concious people?

 

From what I have heard - you will definately notice a difference. I know some Mopar guys that drove their cars to the welders and had subframe connectors installed on their B body then when driving home they said it was very noticable. All for the better too.

 

They do lower the ground clearance. If you cruise the mall, and it has big speed bumps, that could be a problem
Also, running exhaust pipes out the side can be a little more dificult to make look right. Dr. X has some nice ovalled pipe pieces to help.
I did the TCP setup in the convertible, and have fabricated them for other projects. The "X" brace offered by TCP that ties into the subframe connectors is also very helpful.
You need to be careful when welding them in. The frame rails are much thinner (and hopefully older ) metal. The amount of stiffening is exceptional. I can jack the convertible up from any single point, and both doors still open and close correctly. So they do work.
Maier racing has a very nice setup as well. Welds to 4 points on each side instead of just two, so the forces are distributed across more of the uni-body.
There are a bunch of different ways you can do this. Lots of good information in different threads on this subject. I've got a few shots of mine on the web site in my signature. I'm sure if you search around, you'll find much better information, and nicer pictures.

Good luck,