1) Plastic gauge: I bought some as I am checking the bottom end on a motor I just purchased. The way I understand is cut a piece ¼ inch long place it on the bearing, use a bit of lube to hold it in place and tighten down bearing cap then remove and measure. The piece I put is perpendicular to the bearing?
2) Upgrading the top end: If I put larger cam in the motor than stock, (nothing wild looking for 50 to 75 HP gain,, do I have to have different tune, do I need different injectors, throttle body etc. etc. or will the engine see gains by only putting in higher lift cam.
My car is 93Z28 so speed density and no Mass Air flow sensor.
I have always just repaired engines to stock never have thought about increasing HP with internal power adders only have used bolt ons.

My current bolt ons are PCM Chip, K & N Cold air, under drive; hi flo cat and flow master exhaust so pretty stock.

Advice is appreciated

 

Cut it full width of the bearing - it lays across the bearing, and since you don't know what your clearances are, use a couple different ranges of the plastigauge. Measure it at the widest point. There's more precise instructions out there on the internet. For the cam, you might consider 1.6 roller rockers and new springs instead, because you would need those anyway if you did a cam, and by themselves they will give you some good bang for the buck. There's a lot of posts about first mods, so read up on it - it's all been discussed 100 times before.