I think there are some issues in your code.

currentPage, currentBlock and currentContent are magic variable names that's used in a controller action to keep track of the currently viewed content. They are used in conjunction with PageController<T> and BlockController<T>. currentBlockLink and currentPageLink doesn't work in the same way - they are just regular variable names and therefore needs to passed from @Html.BeginForm(...).

However, you can't pass PageData or PageListBlock in BeginForm(...) since they are complex classes, you can send their content links though:

@Html.BeginForm(new { currentPageLink = page.ContentLink })

You're asking if it's possible to put two different blocks (that both expose GET and POST actions) on the same page. One thing that makes it difficult is that blocks don't have their own URL, like pages do. So, you can't post directly to a certain block but you could post to the block controller (which would act like a normal MVC controller). That means that you can't use currentPage, currentBlock and currentContent in your POST action method. To solve this, you need to manually pass data to the POST action the way I described earlier, plus information about the controller and action to execute:

@Html.BeginForm("Index", "ContactBlock", FormMethod.POST, new { currentPageLink = page.ContentLink, currentBlockLink = block.ContentLink })

I have not tested anything written above, but these are observations and solutions I've found myself.