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Building 71, cant decide on motor,choices are ,all cast iron small block with cast exhaust manifolds, cast big block with cast exhaust manifolds, cast bb short block with alumanum intake,water pump,heads,headers. Also wanting to run maual trans cant decide on 4,5,or 6speed, have 3.08 rear gears, also what trans ratios would give best split of gears for accelloration and cruise hoping to run 5 to 6 hundred horse.
..if you're looking to keep your weight limited, which is always a very good thing, you should go with a SB alu heads/intake and ancillaries, it also depends on your budget because an alu world lite blk would also be (very) good indeed, if you can effort it (about +2.500usd on a very good iron blk)
trans: i'm a supporter of the 4 speeds trans, tough, light and enough for good sprinting and if you're not a crusade of long trips cruisings at 2000rpms on the motorways, that is the way to go.
rear gears, i have the 4.11 but i'm a bit extremist , maybe a 3.77 would do well too.
Since you don't have 3 special purpose cars, (one for crusing, one for drags and one for auto cross) then the gears you get are going to have to be a compromise.
I would strongly suggest a 5 speed, if you get a 6 speed like a Tremec or a Richmond they are big and you will have to modify your trans tunnel to make them fit. If this isnt an issue then go ahead with a 6 speed. The 3.08's are a good gear if you have a 5 speed but I suggest 3.77's if you get a 6 speed with a final on the trans somewhere around .64 for the over drive.
As far as the engine goes, or any other part of the car goes, reducing weight effectively increases horsepower. So a world all aluminum SB would most certainly be the way to go. It works out to be about every 10 pounds you take off the weight of the car is good for 1 extra horse power. Just a very rough rule of thumb.
Good luck with the project should be a lot of fun.