Re: "GOING FORWARD IN REVERSE" OZZY Quote
I agree - you did NOT get a '79 lower unit. Finding a counter-rotating prop will NOT fix your problem.
You have two options...
1 - find the correct lower unit. As Ezeke noted, the one you want will likely have a swept back skeg. The skeg with the trailing edge at a 90-degree to the propshaft is the earlier style and won't work.
2 - find the shift linkage from an earlier model. You want the whole shabang - the bellcrank, tie-bars, etc. from the powerhead.
Also, confirm the year of your motor. If you post the model number we can be sure you've got a '79...