Pretty self explanatory title, I'm really starting to dig the tele shape, and I don't have the cash for a US made 72'. So I need to know how to mod the standard SS tele (made in mexico) to an HH dual humbucker set up.
Is there a cavity for a humbucker underneath that pickguard? or would I need to perform surgery on it? and how about the metallic bridge? how do you replace that?
In the end, would it be cheaper just to buy a 72' strat?
Looking at a picture of the telecaster body:

There isnt enough space for any humbuckers, im afraid. You can get Single coil sized humbuckers that would fit, or you could get a 4-way switch fitted for the two pickups in series in pos4. Other than that you'll have to route it yourself.
However, you can get new bridges that have enough space for a humbucker. Its just a case of unscrewing the old bridge, dealing with the ground (may be soldered somewhere, like a strat, may not, im unfamiliar with tele grounds im afraid) and fitting the new bridge. You may have to drill new holes depending on your bridge.
So, there is a lot of work involved, but it will probably be cheaper that getting the 72, as the only parts are the bridge (which is cheap, under £20) and the pickups. SC size buckers/4 way would be less work, possibly cheaper but would sound less like a humbucker.
You will have to route to make the pickup cavities larger. You will also have to buy a new bridge plate. You will need a new pickguard as well. There are several steps, but it's not that difficult if you have a router and know how to use it.