well i got started and i think i have a problem.. i bought 2 pcs 73 in long they told me that's enough to do a 4 door car , is this true cause the math don't add up ,,, and i see the front door front is different than the rest of the channel , so can someone add to this please

thanks

1958 chevy biscayne
235 6 cyl 1 barrel
2 speed PG tranny