I put pyro/boost gauges in my '01 and I swore I'd never do it again. I love the look of analog gauges, but the install sucks. There's not a whole lotta room between the A-pillar and the cover for all the wires you need to run. When all was said and done, the x-monitor would have cost maybe $50 more,partially because I got pi$$ed and broke the first pod.
I ended up being a cheap-***** and putting the same gauges in my '04. 5. I'll say it once more, "NEVER AGAIN". I still love the looks of analog though.
Oh yeah, there is no real visibility problems with a '99. I only had the double, but there's lotsa room in those trucks. Only issue is wiring.