ok, first off, where in the system do you want to use the 1/4 to 1/2?
the proper way to do this is at the tank, replace the fuel sending unit with one that is 1/2 inch right from the get go
the good news is, this is a 30 minute job
the bad new is NO ONE makes em with the proper configuration, so your fuel gauge will be off
(there are a few people who rebuild/modify OEM senders, so that might be a fun winter project)
OER MF259: Fuel Tank Sending Unit 1963-74 Mopar A-Body | JEGS
then you want to run a full 1/2 inch line from the sending unit to the pump
you need to decide if you want a hard line like stock, or run a "flexible" line
i just replaced the one on my duster with a 3/8 preformed line BUT i couldnt get it snaked in so i ended up cutting and splicing it
depending on what you decide, you need to find a fitting into the pump, simple enough
this
Straight Adapter 8 AN to 1/4 NPT Fitting Black HIGH QUALITY! | eBay
or this
Brass Hose Barb 1/2" x 1/4" NPT Male Pipe Thread Straight Fitting | eBay
then you got to run a line to a regulator and the carb
i would suggest braided -8 AN
same fitting as i allready posted
so all you need to decide is, do i want hard line or not?
and dead head or return style?