You might want to really talk it over with the rebuilder, Many will not warranty parts they don't sell.
Also, they can usually beat any price you might get. When I did my jeep engine last fall I bought the cam because it was from a specialty shop, But the builder i used beat the price on all the parts by about 35%. Biggest savings were on the Pistons.
Remember, These guys are making a living, they have to make enough money on the job to live, if you get a low ball price youll likely get a lowball job, Engine rebuilding is a craft, and the extra two or four hundred on the rebuild to have a top shelf job done ins nothing compared to the hassle of pulling the motor again..... Pluss you ought to feel how much difference it made to have a totally B&B'd assembly job. My redline on the jeep went from 5500 to 7000. I don't do that much it makes its best power by 5000
but if I'm climbing out of a bowl sometime I just stand on it to avoid the shift.
BTW anybody in the Portland Or area, I can hook you up with this guy if you want, his main line is race engines but he does street engines too. Guy has super experience and is way cool to work with.