When I was building HEMIs at Mopar Engines West I never put in dipsticks. Most guys are anal about changing their oil and if it’s not leaking or burning it, there’s no point. Nevertheless, I have had customers that demanded a dipstick rather than a blanky for emotional security. To me it’s a potential oil leak, a vacuum leak when running a vacuum pump, and snaking the dip stick around the headers is always fun. But yes, you can add it just by removing the pan a drilling a hole. I’d suggest making sure the new hole is dry and use “The Right Stuff” to hold the dipstick sleeve in the block.