For the little 'startup' phone video above the exhaust consists of the old 2.25" cheap mufflers the car had when I bought it.
I welded them onto flanges and bolted them directly to the headers. Probably pretty choked down, going from 3.5" collectors to 2.25" mufflers! But it still sounds good, and very loud.
For the 'shakedown' video the car had open headers, no exhaust.
As for when the the car is complete I have a nice 3.5" to 3" stainless exhaust I made with Magnaflow mufflers.
It's not on for this shakedown stage as it clashes with the reverse rod of the four speed (I was always going to make a custom rod as I don't like the way the stock one dangles down loosely) and because I need to finalise the angle of the drivetrain and weld on the stainless flanges for where the exhaust bolts to the headers.
Cheers!