I would highly recommend you go on a plains game first. If you have the money to go on a dangerous game hunt then you have the money to buy a better rifle for DG hunting than that NEF 45-70. That would be around my 133rd rifle choice for DG!
BTW, do you know what it cost to hunt Cape Buffalo? Or were you planning for leopard, lion, elephant or rhino?
A 30-06 would be a good choice for PG but is approaching the light side for eland.
You get more bang for the buck by hunting PG. Usually, you can 3-5 or more animals on a hunt. Bring extra money as there might be something else you want to hunt.
The most important thing you can do after you decide is to practice shooting your rifle as much as possible shooting field positions.