Howland source, MAX current output?
The op-amp has to supply all the output current plus a bit for the feedback. So you want to look at the current that the op-amp can supply. In the case of the TL074 it can supply 10V into 2K with a +/-15V supply, so that's 5mA, guaranteed. 

It can probably supply quite a bit more current but there is nothing guaranteed, not even a typical number. 

If you need high output current, you should probably pick a different op-amp with guaranteed specifications in that department. Op-amps such as the LT1014 are often specified with 600 ohm loads, so more like 15mA. There are also power op-amps that can handle amperes on the output stage. Or high voltage.