When I put the 460 in my '69 I installed big block (428) springs. By the time I put the 460 in it was so light that the springs barely compressed at all and the car was darn near undrivable due to the stiff front end. Put in 351 springs with a 1" drop and it sits right, rides nice and handles as well as the 351 - just don't hit the loud pedal in a corner.
The changes I made to lighten it up are the same ones that everyone plans to make to a 351:
Aluminum heads
Aluminum Intake - Edelbrock dual plane Performer (basically an a stock 4V intake)
Tube headers (in my case steel shorties from FPA)
Battery still in stock location, BB radiator, belt driven fan.
Internally i run a small 268*/.494" lift cam, stock crank, stock rods and TRW flat top pistons (9.5:1 comp), melling oil pump, no special machine work. A 750 carb, Duraspark II ignition and Holley fuel pump.
I have a 9" locker with 3.25 gears and Shelby under-ride bars, a C6 with AOD gear set (lower 1st gear) and a 2500 stall. She launches hard on dry pavement but will still smoke them if you tromp on the gas. She will break loose at 30 MPH if you want it to. On (e-free) pump gas.
Okay, so she only gets about 12 MPG, but she is streetable, dependable and a blast to drive.
429/460 parts are plentiful and affordable - I haven't built a Cleveland in more than 25 years, but back then parts were harder to find for the 351C and very pricey. Maybe that has changed.
In any case, weight or room should not be a factor. The 429 was available from the factory and there is a lot more room in the 7123 than the 67-70.
