Bruteforce partial HASH SHA1

hello!
Please advice, i want to find binary password that will produce specific bytes of SHA1 hash
Where to change code in .CL modules to allow compare only first 8 bytes of SHA1 hash?

for example

running hashcat -m 100 -a 3 my.hash ?b?b?b?b?b
i have my.hash with
1122334455667788A1A2A3A4A5A6A7A812345678
and i want to find all 5-byte passwords where  hash will match first 8 bytes of hash
i.e. SHA1(pw5bytes) == [1122334455667788]

Thanks for helping.