Hi Jay, You should be able to use your stock guages. I don't think it would be any easier installing the newer one's but that's JMHO. What you need to do is try to get a wiring schematic or try tracing out and marking your wires. From there you can decide what you need to tie into the harness and what will be standalone with your existing wiring.

Here's a couple of things to think about:
Electric fuel pump and relay
TCC to brake switch
VSS (speed sensor) input to gauge
Tach tie in
A/C request and relay
A/C clutch engage
Cooling fans and relays or optional fan clutch
Cruise control
Starter wiring relay
MIL indicator
Altenator
Neutral Safety switch
Serial data connector and wiring

You can use the wiring harness that came with the motor or get Allen to build you one.