Once you have it running right you will love it. I have an H55-F in my 1987 FJ60. It is the best conversion possible in my opinion. The truth is the H55 was designed to go in later model FJ-40s and 60s and some light-duty Hino trucks. It is still manufactured (obviously) and used in the 70 series, Hi-Lux, and Hi-Ace trucks- can't beat a great design. Back in the late 70's and 80's Toyota opted to exclude the fifth gear on the North American models because of the 55 mph speed limits in the U.S. and parts of Canada at the time. The 55 mph mandatory national speed limits were lifted in 1988.
You will experience this (sorry I don't have the ratios, this is more of a feel thing):
1st- Is definitely lower than the original 4 speed. It's like granny gear in old trucks, but not quite as low. You will top out at 4000 RPM & 10-15 mph
2nd- You can start in second gear on a level plane or down hill. It is higher than the original first, though not quite enough to start on a hill unless you slip the clutch a lot. You will top out about 25 mph.
3rd- I call this the neighborhood gear. It is great for cruising at 35 mph and tops out about 45.
4th- This is the gear for driving in crappy speed limit zones or where you stay when you forget you have a fifth gear. It tops out around 60-65 mph and the engine roars.
5th- Cruise comfortably from about 50 mph to 80 mph. At 75 mph the RPM is about 2700 The FJ-60 handling above 85 mph gets squirrely, I usually don't go above 75 mph... not much for aerodynamics there.
You should expect 14-17 mpg in the city and about 20 on the highway. I average about 17 in combined driving, which is better than before the conversion.
Trust me you will love it. Oh, and one more thing... it took mine about 10K miles before it finally loosened up. Before then it was tight i.e. hard to get in gear at times.