Looks like the Mercedes gauges are a no go. ;(
Got a response from Palo Alto:
"I will not be able to re-screen the gauges that you currently have. The Mercedes faces can only be installed on to Mercedes gauges.
The best gauges to use are the 914 gauges. The cost for a replica 356 gauge set is $2,200.00 + shipping. The lead time to build a set is 8 weeks"
When I compare that against these - for 1k :