I've been running a hopped up 350 for years using the ORIGINAL guage..... HOWEVER, I had a local shop, D&M Restorations re-calibrage my guage so that what ever it reads the pressure is actually double. So, when it reads 15lb its really 30 and when it reads 30 its really 60. I wanted to keep it original but ai also wanted to know exactly what my pressure is.
Its ot going to hurt your guage to ped it out but if you want to know exactly what the pressure is you'll have to do something.
I think the 39 guages are the same as my 37. I found out to late but you can use the guages out of a 260Z and have instant 12 volts stuff. All you have to do is snap the bezel around the "Z" guages and you have it made. If you can do without originality I suggest that. Go to a junk yard for imports and get the complete set for cheap. Heck a guy even gave me a set. Different years hae different color combo....some black dial,red marks..others may have white dial with black or red marks.
Here is a pic of what I'm talking about.
http://i140.photobucket.com/albums/r19/LutherParris/52Panel/picsforphotobucket005.jpg
