a duel polarity power supply in LTSPICE

Need a Howland constant source grounded load as well as a duel polarity power supply with a ground.
Going to use 7805 and 7905 on the 12v outputs of attached circuit but how to compute current available at outputs?
Using LM324 op amps
don't want to use a CT transformer as I have a 24v transformer w/o a CT (using from existing temp soldering iron)

Why not use LTS to compute the current available, using dummy loads? I see you have a .step command with a parameter R, but where is {R} on the schematic? Ultimately, current available will depend on what your tranny can provide and on how much ripple you can tolerate on the caps.
BTW, why not use a bridge rectifier? As shown there is only half-wave rectification and one of the diodes is superfluous.

The schematic was copied from another post and failed to remove all of not wanted components.
LTS and dummy loads?
Not real familiar with LTspice but learning something every time I use it.

Stick with LTS. It's a steep learning curve. Just add varying load resistors to your sim supply and monitor how the reservoir cap voltage is affected.

Going a different direction by using an LM317 for a constant current source