In what gear? Its really high for 5th. Stock is closer to around 2400rpm at that speed.You should check your gear ratio and compare that to your tire size. The prior owner might have had bigger tires and lower gears, but downsized the tires before selling the truck.
I agree with showstop. 3200 sounds high.
Due to possible changes in in final drive ratio with gear or tires, the first thing to check would be that your speedometer is accurate.
Most car GPS devices will tell you your accurate speed.
If not, you should be able to find a free app on your phone.
I use "speedometer" for the iPhone.
Once you know whether or not your speedo is accurate go here:
Heres some instructions:
Step 1 on the left: Input Toyota R150F
Scroll down to step 4 and input what would be the stock gear ratio for that truck: 4.10.
Step 5, put in your tire size either in inches or P-metric dimensions. IE 33" or 285/75/16.
Once those 3 things are input you can scroll down to the 3rd chart on the left titled "Road speed at given RPM in miles per hour"
There are 3 rows and 5 columns. Set the middle column to 3200 RPM and note the road speed for 4th or 5th gear.
If the numbers don't match up, try changing the rear end ratio from 4.10 until your numbers do match up. Popular ratios for Toyota's are 4.10, 4.30, 4.56, 4.88, and 5.29.
Example: if you have 33" tall tires and 5.29 gears in the diff, you would be at 59MPH in 4th gear.
Example 2: if you have have 31" tall tires and 4.88 gears, you would be at 60MPH in 4th gear.