If you’re doing this cos you’ve got the 26″ bits and can’t yet afford the 29er equivalents (wheels, forks), which is the only reason I can think of to do this, then it might be doable to use the wheels- if you pick tyres carefully you might only lose an inch off the bb. I think using a 26″ suspension fork might be a step too far though- at the least you should get a rigid fork with an a-c suitable for the frame, so the geometry doesn’t get too f*cked up.
If you just think it’s a cheap frame and you’re long term intention is to run it with 26″ stuff, don’t.