Hi and welcome to the forum!
Why up to a 1974? Is this for tax free? In case you aren't aware of the differences, early bays go up to 1971, then you gate the cross-over with a later rear end setup 71 > 72 (I find the most commonly available due to the larger production numbers in this year), then after 1972 it's a late bay and we don't like to mention those :lol:
I'd firstly think about LHD or RHD - one comes with a premium, but you can get more bus for your cash with a LHD - then conversion/model which will be driven by LHD or RHD (e.g. a pop-top westfalia will cost ££££ more in RHD than LHD due to rarity), does it need a pop-top? are you after original condition or are you flexible with any upgrades, in which case you could go for a converted panel van rather than an original camper layout from factory
When do you need it on the road? Straight away or if you are prepared to wait for the right bus, then importing a peach from south africa (RHD) or US for LHD is possible via a number of trusted importers on this forum
If it helps - I worked out the type, year, model, then condition and waited around 4 months for one to come up in holland, had it imported and MOT'd and found this to save having to go around looking at campers, when someone you can trust will look and advise on your behalf
Anyway - hope the above helps