Long-off 340 build

If going the hydraulic roller route you will need to inspect the lifter bores on your LA and see if they are chamfered or not. Depending on what you find you will need to either bush the bores or, an easier way, use the Hughes rollers that have the lowered oil band.
Hughes Engines

With regards to the 408 comment, I believe chrispy was referring to a stroked out 360. Also I think Blueprint uses Magnum blocks (LA based and a small block).