My 69 has a 72 340, SpeedMaster heads, Power Steering and Doug's D453 headers plus a Z-bar and a TKO600 and it all fits fine. You will need to check clearance around the Power Steering box and possibly shim the motor mounts for clearance once you verify the ending is in the proper location. Use good header gaskets, I used Remflex. Get a mini starter if you don't already have one.
Not sure there is another header that has more clearance other than fenderwell and possibly shorty TTI's.