Would A Street Triple 675 2007 - 2012 Engine Fit In My 1999 Triumph Daytona

If it was me I would be looking for a 955i replacement engine.
trying to retro fit a 675 engine in that frame would be an absolute Ballache for little gain IMHO

 

Even if it fit (and I doubt that it would) you would need complete wiring harness and ECU plus a host of other bits
Even going to a second gen 955 engine (02-06) is not trivial (that series of engine will fit the frame but there are a TON of other things that need to be replaced along with it, again you'd be looking at wiring harness and ECU but that's is only the start) - stick with Speed Triple (99-01) Daytona (97-01) or Sprint (99-01) or it's going to be a whole lot more involved

 

Nothing is impossible, but it’s if the gain is greater than the pain.
I’d look for an original at least you know it will go. But if you like a challenge as I say it won’t be impossible