I did this on a 70 Challenger went from a 22" to a 26" radiator. Bolted the stock 26" radiator in on the drive side using the factory bolt holes. Drilled new holes on the passenger side core support to line up with the radiator mount holes. You will need to add washers or make spacers to get it even on the passenger side. You can cut out the passenger side core support opening to get more air flow across the wider radiator. Doing this I used the stock shroud and fan and they lined up perfectly. If you want the original look you will have to replace the passenger side core support. If you make nice spacers that run the full length up and down on the passenger side radiator mounting flange and cut the core opening wider it looks good.