HELP PLEASE "what engine for a 1973 camper"

[73 Westy]

I have a 1973 T2 Westy and the big end has just went in my 1600 tp so I need a new engine. A new stock is going to set me back £1000 so I would like to consider an alternative so I can get the power upgrade I have always longed for, and then I can use the van as a daily driver and sell the car to pay for it all.

I don't need anything excessive, I just want to be able to sit at 70 mph on the motorway, regardless of hills and get some reliability. I would prefer to get a porsche engine to keep it aircooled and use the same gearbox + breaks but I am at the mercy of my budget which can't stretch beyond £1500 - £2000 for the engine including fitting as I have already spent £1500 on the resto over the winter and she still needs a full respray.

Can someone please tell me which engine would be best for my T2 Camper, how much extra modification or problems I will have to get it running and where to start looking as my resto is nearly finished and I need it ready for the summer

Many thanks for any help or advice as it is urgently required.

David