You don't need to be an 'investor' to invest in Singletrack: 6 days left: 95% of target - Find out more
Ignoring discussions about precision and accuracy, always makes sense to use the same shock pump for repeatability, but depending on your fork/rear sus the std 0-300 / 0-360 psi gauge might be a bit wide for your app. to add repeatability think it helps to have a bit better resolution - i don't need more that 80 in forks or 175psi at the rear.
The Rockshox (and all that the same design) seem to use a 1/8BSPT gauge. Swapped mine for a 0-200psi to improve the resolution a bit - £5-8 from ebay and probably of equally crap quality as the original.
[img] 
[/img]
Does not work for Topeak pumps as they use a press fit gauge.
ps ebay link for new gauge:
https://www.ebay.co.uk/itm/233652733229?hash=item3666c9c52d:g:Ih4AAOSw6g5fEcNq
But...The original has a red dial, so surely that means it's faster?