Factory style hose clamps
Wow.
I've never had to use any type of sealant on a radiator or heater hose (in over 35 years).
Last year I put my 73 318 back in and used ebay sourced OEM style clamps on a combination of used and new hoses. I only had to use screw clamps on the bypass hose because of the A/C bracket and no space for the pliers.
The only issue I had was the clamps didn't open quite far enough, requiring me to work the hose into them while holding them open. Not terribly fun to do with one hand.
No leaks.