Mopar Stage VI 6 heads questions

The amount of valve lift it can take is related to the valve length used combined with the spring height, retainer and the valve seal height. I’m sorry that wasn’t specific but the parts used on the head can vary a lot.

I don’t know about rocker offset.

I’d say yes to custom length pushrods as a better than a 90% probability. Considering your not using a stock can and the rocker may not be the same or in the same exact place as the stock rockers.

The head was designed within the confines of the stock architecture, hence there limitations.