considering using an alfa romeo box and diff for sunny race car, can get a 5 speed and good price for box diff and inboard discs like $950. thoughts that crossed my mind.
a) would decrease unsprung weight
b) change weight distribution of the car as gearbox is rear mounted, also meaning i can set motor back on crossmember a few inches without having to make large tunnel in middle for bellhousing.
pic of 1 is here http://www.hiperformancestore.com/images/gtv6trans.gif
of couurse not use their heavy weight suspension system, instead i think fabricate some wishbones and coilovers
any thoughts on this idea?????

First things first, when you say race car, do you know what category you want to run in? If so, check the rules for that category. There are not too many classes I can think of that would allow you to move the gearbox to the rear in that fashion.

from looking at cams manual, i think i can do this in sports sedan 3d, seems chassis and motor setup is pretty free. would be an easy conversion if fabricating a full chassis car i intend to use only the bodyshell fron my b310

4.3 Transmission: The design of the transmission is free, save for the following:
• The clutch must be controlled exclusively by the driver by either mechanical or hydraulic actuation. The use of any electronic clutch actuation systems is prohibited.
• The gears must be selected by the driver exclusively via a mechanical linkage.
• The use of any electronic, hydraulic or pneumatic gear selection device or assistance is prohibited.
• A gear lever-mounted switch, which must only provide a gear shift cut signal to the ECU, may be fitted.
• Four-wheel drive is permitted on cars originally produced in that configuration, however they must remain in “floorpan” construction and retain the original engine block and cylinder head/s for that particular vehicle model.
• An operable reverse gear must be fitted.
• The maximum number of forward gears shall be six.
4.4 Engines:
(i) Engine and ancillary equipment is free, provided that:
• the engine block is derived from a car eligible under the provisions of Article 2 hereof;
• the road use mass-produced three-rotor rotary engine assembly is acceptable (Mazda 20B);
• all engines must be front mounted;
• it is sourced from a series production vehicle of which at least 2500 examples were built; or,
• it is permitted to use a cylinder block manufactured by an aftermarket supplier provided that:
(a) it is an identifiable replacement for a permitted, original equipment cylinder block;
(b) the centrelines of the crankshaft, camshaft, and lifter bores are in the same relative positions as per the original equipment cylinder block; and
(c) it is made from the same material as the original block.
(ii) Engines mounted in the front (subject to the above) may intrude into the space originally intended for passengers, save that no part of the cylinder block may extend across a line drawn at right angles to the longitudinal axis of the vehicle at a point halfway between the front and rear wheel hub centres.

As has been previously stated:Reasearch,research and more.
You also need to decide if you want to actually race this thing before your a grandfather(assuming your not already)and the rules change again.
Or if you are just keen on the building side of things.
Either way get down to some events at QR and Morgan Park next year and talk to owners/drivers and keep us informed on your direction.
Cheers

When I first read your initial post, I was thinking Sports Sedan would be the only option.

If you are going to the trouble of building a full chassis car, why would you not go for Fibreglass body also? Lighter than the original.

i tossed around the concept of fibreglass body for quite awhile, to racein the class i need a car weight over 780kg as a sunny starts at 610 and i will be removing lots of interior and trim and steel, i am not sure the rollcage and new chassis will be enough to get a glass body over that and besides i think if it came to it i would rather roll over in a steel shell..