There a quite a few DIY dynos that have been made for go-cart engines. SOme are simple hydraulic pumps based brakes and others are flywheel based intertia dynos.
A friend made an intertia dyno for testing go-kart engines and found suitable data acquisition equipment on the internet. I think some of the links are/were on/off the 1/4 midget association website.
Do a google for "go-kart dyno" and you should find a phethora of links.
Data acquisition for go-kart versus V-8 engined stuff is essentially the same. However, power absorbtion becomes the hard part.
Inertia dynos for engines that develop major amounts of power are very serious beasts. Not only is the speed of the flywheel an issue to deal with but mounting and containing it is NOT a task for hack and slash lightweights. The amount of power in even a 200hp engine's flywheel running at peak torque could put enough energy into the flywheel that would put it thru a wall and into the next county if it ever got loose.
We learned a very valuable lesson with 0.05hp R/C car motors and inertia dyno flywheels we were playing with at the time. The flywheel of the dyno came loose. The guy was using it in his den on a desk top.
It flew off the motor, danced across the desk, gained traction and ran across the room taking out the TV in the process. It then went on to climb up the wall paneling before it poked a hole in the ceiling. And that with only 0.05hp.
I think that Professor Blair has an SAE paper with a psuedo "how to" on a go-kart dyno. It might be scaleable to a V-8 if you can find suitable absorbtion hardware.