I had an original early GMC gauge that would have been a bolt in swap, only it wouldn't read anywhere close to actual numbers. The inner workings were full of dried up oil I could not get out. I tried for weeks soaking it and never could get it to work. I drove my truck for 20 years with a 30 lb gauge with no issues, once i installed the high pressure gauge, the oil pressure didn't go much over 45 on a cold start and runs around 30 while driving, so it wasn't pegged, just at the top of the scale. 250 inline six with 5w-30 full synthetic oil.
