Piston rings on 440 invader

[Hunter]

Ok so I ordered a set of pistons off of eBay for my invader. I tried to assemble the top end last night and realized that the rings are too large to fit correctly into the bore. It's very difficult to get them started in the cylinder in the first place, and when I finally did get them into the cylinder it was so tight that I'm sure once the engine was up to operating temp it would seize.
So I did some digging and found out this piston kit was made by Parts Unlimited (guy I bought them from didn't say who the manufacturer was) and right on website it says "rings are not OEM style and will only fit parts unlimited pistons".
So out of curiosity I put the rings from the old pistons on the new ones and sure enough the pistons slide right into the bore just as it should.  So question is what company do you buy your rings from? and do you think I'll be ok using these pistons or should I just buy a new kit form a reputable company?
Sorry for the long post.

[gixxer6]

It sounds like you just need to adjust the ring end gap. 

[Hunter]

Ok what is the end gap supposed to be? When set side by side the new rings are definitely larger than the old ones, ring gap is about twice as big.

[Interceptor398]

Ring end gap on an Invader is .008-.028 while resting in the bore.

[Boomologist]

Also, verify ring height. If too short they will hammer out the ring grove, break and ruin piston and cylinder. If too tall they will get warm and stick in the grove. Depth into the grove is also critical.