Stay with straight plugs. Angle are a royal pain - especially with headers.

I have installed lots of new lifters on existing cams and had pretty good luck with the following method:
1. Clean the new lifters with mineral spirits. Don’t use paint thinner or gasoline. Mineral spirits are made of 100-percent petroleum distillates and has no additives or gunky stuff. Costs about five bucks at your local hardware store.
2. Dry them thoroughly and then place them in a container full of oil (same stuff you use in the engine).
3. Coat the bottoms with assembly lube. I use COMP Cams 152. Its $15.95 on Amazon or you may be able to get it locally.
4. When you install the lifters, they should slide in nice and easy, and you’ll hear a little “tink” as they contact the cam.

Adjust the valves to zero lash (push rod is hard to spin between thumb and forefinger) and keep it loose to start the engine. Easiest way is as follows:
1. Bring #1 to TDC (compression stroke)
2. Adjust the intake valves on cylinders 1, 2, 5, & 7 to zero lash.
3. Adjust the exhaust valves on 1, 3, 4, & 8 in the same manner.
4. Rotate crank 360 degrees to get cylinder #6 to compression TDC
5. Adjust the intake valves on 3, 4, 6, & 8 in mentioned manner
6. Adjust the exhaust valves on 2, 5, 6, & 7

Once you start the engine, slowly work them down ½ to ¾ turn from zero lash – no more. Only go until the valve is quiet.

Let us know how you progress and be sure to post some pictures!

Glenn