One of the strongest arguments in favor of the beam is that GM already did all the work - can't be too bad, and whatever it's doing is easy to diagnose. To improve: lightest wheels and tires you can find, and the lightest spring that never bottoms (or crashes the bumpers). If this lower the front too much, use a longer but smaller diameter spring.
An IFS can be installed wrong many different ways.
1. if the wheelbases don't match, or the IFS is not installed with the axle center in the same position, the Ackerman is wrong (an inch or 2 is harmless, a foot affects long speed turning and inside tire scrub)
2. the chances of weight distribution being the same between the donor and the Chevy are not great, which means the donor sway bar is not the optimum rate
3. chances of inheriting some bump steer is fair to good, and should be fixed (typically by moving something up/down)
4. for best alignment and tire life, use the donor wheel offset and tire OD to remove some variables
If the shock gets too hot (the paint shouldn't really burn off - but does happen to race bikes), stiffening the spring will reduce this by reducing travel - at the expense of ride quality and making the chattering worse. The cure is to reduce the unsprung weight, or increase the shock capacity (typically larger diameter).
