Greets! I have made a search of posts but haven't found anything...

I fully understand "Not 5V compliant" pins is not to be trifled with - so just to be sure - if I want to use the T4 to access other boards (Like CP104 USB-to-Serial) should I get a bunch of decent level-shifters and have any pins going to a 5v board go thru them? I don't like "shields" and tend to tinker-toy with various functional boards on a solder breadboard for final build. All the boards I have now were used with Arduino boards, so the 3.3v is a new concern.

I did see that Paul mentioned some level-shifters that use MOSFETS are too slow.. I'd prefer not to mess around trying resistor combos... any recommendations on packaged units?
=A.