mine is a fairly good spread of light changed over T5's and T10s with cheap ebay wide angle white superbright bulbs fig1.
no real dull spots, altho around my fuel and temp it looks alot brighter due to the closer proximity of the bulbs in that area
other than that very good visability and brightness, very crisp clean more modern looking cluster
fig1.
its a bit of a custom mod what you are thinking of doing... it can be done but u gotta have a good plan, also maybe a spare cluster to test it out on 1st (pick up from wreckers)
just need to be aware that there are clear plastic light reflectors all through the inside of the cluster which are positioned to spread the light from where the stock bulb positions are
fitting the extra bulbs in may be a tight squeeze along with their wiring
very much recomend using proper T10 and T5 sockets, for better safety and easy plug and play with different bulbs
but yeh dont think anyone else has done this sort of thing b4 so make sure if u do do it you write up a diy on putting in the extra bulbs
for another route, you could look into jap evo EL style dials, these are however expencive and i dont know anyone who has bought them