There's a bracket between the block and turbo, at the back under the manifold. I may be wrong here, it may run between block and manifold - it's been a while since I attacked one - but it's cleverly hidden from view though plainly visible from underneath. The turbo may be a tight fit on the manifold since the manifolds are prone to cracking and may be somewhat distorted at the flange because of that. If the replacement turbo is attached to a manifold and that manifold isn't cracked I'd replace them as a unit.

As for the crush washers, if you can't get them at the dealership try an auto parts store, they usually have a selection so take in the old ones to match up. There's also a gasket you'll need between the turbo and the oil return pipe on the bottom of the turbo (if that's been removed), and replace the seal at the block end of the return pipe. It can be tricky getting that o-ring to seat squarely in the hole in the block, so pay attention to it when the time comes - or you'll have a persistent oil leak there.
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Chris, Dartmouth NS Canada 70 M-B 280SE, 83 245DL, 84 244 turbo, 90 780 turbo, 92 VW Golf, 90 740 Rex/Regina