On 79xx series the lead configuration is common/in/out when viewed from the package side (c.f. in/common/out on the 78xx). The 79xx heatsink tab is also connected to the input connection so an appropriate heatsink washer / insulated mounting-bolt/nut will be needed:
http://www2.ensc.sfu.ca/reference/da...ets/LM79XX.PDF
Apologies if this is 'grandma [grandpa?] & eggs' ...
O/C, if you decide to go down the 79xx route - should you need them, send me a PM with your postal address as I have a few TO-220 heatsink washers somewhere (and the little plastic 'top hat' insulators for the mounting screw) that I'd be happy to send you FoC
All the best
Guy