Heat Exchangers for a 914-6 GT with a 3.0L Options

[Tom1394racing]

Anyone have any suggestions for heat exchangers that will work well with a 3.0L. Or...Can anyone suggest an alternative to get some heat in the cabin while using headers?

[horizontally-opposed]

With Ben out of the game, I'd stick with headers—and go with MSDS Inc.

As for heat, I only need to keep occupants reasonably warm and the windshield clear, so I'm probably sticking with headers. Also, "heat bleed" down the longitudinals and into the car was a thing when I had a four with SSIs, even with new flappers. Wasn't great on hot days, so I bought seat heaters and ordered this to play around with:
https://www.amazon.com/dp/B09N6KN65L?psc=1&...product_details

It just arrived, and easily fits into the space on the passenger side of the gas tank w/o a windshield washer reservoir. Or maybe it goes under the dash—the more heat in the cabin, the better. Thinking about a factory rear defroster switch to turn it on/off. The draw (and safety!) has yet to be figured out with heated seats and decent audio. I'm running a high output 911 alternator, but…