You're probably better off buying everything from the US. The biggest challenge will be deciding between all the upgrades that are available!
Here's a couple of starting points;
https://www.manciniracing.com/bengineparts.html
https://www.summitracing.com/search/...-size/6-3l-383
However there are many sources. Just google 'mopar 383 engine parts'
Just be aware that non of the after market exhaust manifolds are likely to fit, so plan on using the original manifolds that came with your 411. They are perfectly capable manifolds.