GRM has a nice article on MIG & TIG welding this month. TIG welding is a bit nicer, but more operator dependant to do well, and slower. In the hands of a good welder, TIG welding gives really nice welds like this one from my Bennington Motorsports cage:

Does the a/c and heater core need to be disconnected in order to remove the center blower under the dash. I am at the point of getting the Knee bar installed and trying to sort out how the bar and blower can both be used. Will be putting the stock dash back in for now. And at least for the time being would like heat an a/c to stay.

When I gutted my interior, the whole kit & kaboodle came out as more or less one piece, though the heater core and a/c evaporator came out as separate pieces. I suppose you could put them back in after you're done, but its such a PITA to rip all this stuff out, I would just plan on bypassing those pieces and calling it good.

Dumb question - are we talking about the same blower assembly that you tear out in the engine compartment? I know that there are some other pieces under the dashboard for air distribution, but I remember the main blower being the only substantial fan.

Not sure about making things fit, I've never seen the innards of a car w/ a knee bar. Hope my ramblings are helpful, in any case.

IIRC the fans are under the hood and heater core/AC is inside. They must be split apart in order to remove them. It's a PIA to take all this stuff out so if your going to remove it, I'd just leave it all out. You'll also save some weight by leaving it out.