hey & welcome, you may get some good advice on this forum, but i will do my best b4 you get misguided.
you need to have a machine shop bore you 350 .030 over. then you need to purchase a 383 crankshaft which is really a 400 stroke = 3.75 but it has the 350 journals. (it will bolt right up) get a 400 balancer for the front, and use a 350 flexplate in the rear. as the crankshaft should also be a 1pc rear main seal.
that and a cam a little bigger than what you got or better suited for your needs, you want a small duration since you want bottom end and tq. PM if you have more questions. but i got a nasty 383 stroker and its no 350 by all means.