Replacement plug caps

I had those old odd looking radio screened plugs in my 1955 s1 2l petrol, just swapped them out - they are a major pita imho - put in some ngk bp5es, the new ngk plug caps don't seem to fit tightly but the engine runs fine.

so I might get some champion caps see if they fit more tightly. the ngk have a 500k resistor in them, does it matter on so old an engine if I get resistive caps or not please?