BoostedS95

Greetings all, I recently bought a 1995 SC300 with a 2JZGTE swap converted over to a single 61mm turbo. For now, it's making 392rwhp at 18psi. I'm new to this platform as well as what's under the hood. I'm experienced mechanically but this is a new start for me. I plan on swapping out the W58 for an R154 and the stock rear for an automatic TT Supra one. Don't know how long what it has in it now will hold up before it grenades. I've noticed the Tachometer and Speedometer work intermittently. Sometimes they'll come on or one will come on during a drive, other times not. What could be the cause? Will i need to pull the instrument cluster and replace it? No lights burnt out, just the two don't seem to want to work all the time.