If fan blade OD is within the radiator fins and you have it at 1" from rad, that should be OK. No one can tell you if you need a shroud except your temp gauge. Drive it and you will know when summer comes.
The earlier temp gauges say 100 and 212 on them with a 180 middle. Some say 100 and 220 with 180 middle. I don't think much changed regarding motor and cooling system in 54 except the cap went form 0 to 4 lb. 4 lb allows a higher boiling point. The radiators are the same. Same middle temp.
The 54-early 55 "original" gauge is just "C" and "H". I would figure that is 100-220 with 180 middle. Close enough for Government work.
Now for reality:
Your motor came out in the 60's. Has a different sender and gauge. Electric not mechanical. 12V. 7-13 Lb rad caps, different radiator and cooling system....and as you have found out with the motor swap, it sits in a different spot relative to a 54 radiator location. So all the more reason to do your best and wait and see. Nothing bad will happen.
Study before lowering radiator. Could be hose clearance/routing issues or air bubble issues. I say, could be.
