Aftermarket gauges into stock bezel? (64 Valiant)

1964 Valiant convertible: I would like to put an aftermarket voltmeter and coolant gauge into the stock gauge bezel, in place of the stock ammeter and coolant gauge. I have ordered the DemonIVR and plan to get new bulbs and gauge cover stickers. I plan on cleaning and freshening up the cluster. I want to bypass the "fire hazard" ammeter and replace it with a decent voltmeter. I would also like a better coolant gauge that gives more info than just "C-H". I am not trying to "restore" the car, as my goal is just a fun weekend car.

I am asking because I plan on pulling the gauges in the next couple weeks and restoring the cluster on my own. I don't want any gauges mounted anywhere outside the stock gauge bezel, if at all possible.

I've searched around and most direct gauge swaps I've found are on newer a-bodies. The only advice people have given to others in a similar situation is to send the entire cluster out to be restored and upgraded. I don't think it is practical to spend $6-700 out of my budget based on my goals for the car.

Has anyone done this or does anyone have any advice or ideas?

(i typed this on my phone, so I apologize for any grammatical errors)