Apistogramma Borelli Compatible With Bolivian Rams

Personally I think this will be fine space wise in a tank that size. The problem is that your current pair will be used to thinking the whole tank is there's and you are introducing an imposter!  Would it be possible for you to rearrange things in the tank slightly prior to their introduction to allow new territories to be formed by both species?

4 ft (120 cm) is the absolute minimum for 2 different species of south American cichlid. You might get away with it, but have a back up plan in case the apistos object. (Just a side note to say that even huge tanks are not suitable for kribs plus a south American cichlid).

Make sure you get a bonded pair of Bolivian rams. They are incredibly difficult to sex when juvenile - and the fish in shops are juveniles. Even with adults the only sure way to sex them is when they are spawning.
If you got 2 female Bolivian rams, that wouldn't be too bad. 2 males plus the apistos would turn the tank into a war zone. Even a non-bonded male and female could cause problems as it is not unknown for a non-bonded pair to kill each other.
Stand in front of the shop tank quite motionless until the fish forget you are there. This could take up to half an hour. Watch the fish. Males will charge each other and butt each other. Females will just get on with life. If a male allows one female to stay near him without chasing her off, this is more likely to be a bonded pair, though not guaranteed. Take a friend with you when you go shopping and when you have spotted your pair, don't take your eyes off them and send your friend to fetch an assistant.

The trouble is that any future Bolivian rams might want the same end of the tank. This is why I say to have a back up plan before buying the rams