The 1405 is calibrated rich from the factory as it's a performance oriented carb. (The 1406 is basically the same carb but calibrated leaner for better fuel economy.) So, you're on the right track by leaning it out a bit for higher altitude, provided it still has the factory jets/ metering rods etc. Here's a link to Edelbrock's site
http://www.edelbrock.com/automotive_...carb_faq.shtml which says to compensate 4% for every 3000ft.
Here's a simple and inexpensive fuel pressure gauge.
http://www.summitracing.com/parts/SUM-G3122/
and inline hose adapter
http://www.summitracing.com/parts/SUM-G1710/