Combo for back-up motor

[nikk]

I am wanting to build a back-up motor for a open rule modified.I have a standard bore 400,checked by a machine shop(verified good)A set of 034 bowtie heads,.537,.557 flat tappet cam and lifters(used)oem 400 crank.These are things that I just had laying around,what would be an economical way to put some of these parts together to make a good back-up?1/4 mi,med bank,4-bar mod.(gas carb.)thanks.

[hpontap]

Stud the mains and put a decent rotating assembly in it. I would not use the OEM cast crank at all.
Nothing worse than hurting your good motor and breaking your back-up too.

[nikk]

If I have to buy the whole rotating assy. anyways,what stroke would be best for this small cam and unported heads?750 quick fuel carb.what kind of power would you expect?thanks