wow tough question!!!
after carefully reading and re-reading your post several times over and giving it a lot of thought I think I would go with the 346 stroker build, and here is why
1: you are only building a backup engine to have in the unlikely event something happens to your 360
2: your current 360 is already at your target HP with no problems
3: you already have the MP forged stroker crank, and any build will require buying pistons and machine work
4: if your block came with 302 heads then it should be roller cam
5: time is on your side, there is no rush to finish the build so you can take your time and do it right,
6: the increased compression over your stock 360 combined with a roller cam should easily out perform your current setup
my thoughts on option 1 and 2
option1: put the 318 back together and use it while you re build your 360, then put the fresh re built 360 back in
option2: why buy another 360 when you already have one, see option1
