Gimson Robotics was responsible for the GR02 series of gearboxes which many robots still use so I'd guess these will be ok.

However they have a very high output speed, 1500rpm at 18V (you will loose some when you put it under load), so you need to choose your wheel size carefully.

https://wahiduddin.net/calc/calc_speed_rpm.htm

Using this calculator, you can decide what wheel size you want. Most FW's have a max speed of between 8mph and 12mph. Remember if you have a higher top speed it will take you longer to get there.

If we assume the motor does 80% of its no-load speed when loaded, you get 1200rpm. On 3in/75mm wheels that gives ~10.5mph. So with 4 of these together that should make quite a fast and reasonably powerful pusher.

Make sure you support the gearbox and motor properly else you may find the motors coming away from the gearbox.