FF you definately got "Mad Skeelz"
Questions about your guage setup:
Are you going to use any other functions of the later model instrument cluster PCB?
Also that PCB was originally mounted in an enclosure with in the dash, how do you plan to mount it in the Minx's dash and you plan to conformally coat it?
And lastly, is the RS-232 connector isolated from the PCB? I see you're using nylon washers on one side but on the other the connector's metal case looks asthough it's sitting directly on the PCB, straddling 2 copper planes as well as several smaller traces. The reason I mention this is that vibration could cause the connector's conductive case to scratch through the solder mask and ultimately causing a short.
Potentially causing you problems and headaches.