Sorry Earl,
I didn't see this post. You told me you had posted, but I didn't see it.
I believe the 2.9 valve is .030 shorter than the 2.8 valve, but it won't hurt anything. The hardest thing to do, is blend the bowl to match the larger diameter valve seat. Jim has done a bang up job with his heads, and the amount of power his engine is producing, shows that. Jim will also tell you that it is a bunch of work to port a set of iron heads. I have never had the patience to sit for hours wielding a hand grinder to do the job correctly, so I have a professional do mine. You can get away with just blending in the bowl and not open up the ports, but you won't get the full benefit of the larger valves. When you assemble the engine, be sure to blend the ports with no gaskets hanging into the ports, to disturb the air flow.
The rest of Jim's advice is good too,, so send your parts to Delta Engineering to have them rebuild the rockers, and don't forget to send them your lifters and cam, so they can reface the lifters and regrind the cam. I would suggest having them grind the cam to the following specs: 290 deg. on the intake, and 280 deg. on the exhaust, (these are advertised numbers, not at .050 lift) with as close to .500 lift as your cam core will allow. Install the cam straight up.
Don't let anyone tell you that this cam profile won't work, because I have been using it in all my engines since 1975, with great success. You might want to ask Jim E. what he thinks of it.
If you do all these things, you are in for a piece of work, but I can gaurantee you will be happy with the way your 2.8 performs. Another thing, have the heads milled no more than .030, but have them milled, to gain a half point of compression. The stock compression is 8.0, so can use a bit of help. You might also have the block deck trued, but would be careful to not take more than .020 off of that surface. You should check the clearances of the valves with clay, before final assembly, to assure yourself that you are not going to have a problem. Of course, this should be done anytime you use a high lift cam.
Jose