Thanks for the input. The crack is on the left side of the block, some off center towards the rear and about 4" above the pan flange. Everything I read about water glass didn't mention the need for hi heat to cure, so that eliminates sodium sil, which I was pretty decided on anyway. I've located a 248 engine as a backup and still have my old 228 crank, rods and pistons if I can't find a good 270 block. The machine shop that did the work on the 228 has done the metal repair on another job, so he may still have the tooling if Lock and Stitch will sell the screws otherwise there is probably a machine shop around that can do the job. Another potential problem is whether they can do it with the engine in the truck without removing the left inner and outer fenders and manifolds. Just more fun.
Bill