I believe it will be difficult to get 2,900-3,000 fps from a 20" 1x8 with 68 Hornady. My Savage bolt 1x9 with 22" will just get 2,925 fps with 26g of Varget and 69 Noslers. I've tried TAC, IMR 4064, Benchmark, and IMR 8208 XBR and can't get better than 2,800 from any of them without going overmax.
Perhaps you can get there with H4895 or maybe A2520, but I still think it will be tough in a 20". Maybe somebody who has shot them can give you some data.
There are lots of good bullets in between 40 and 68-70. Just wondering why you don't try the new 53v-max with high BC. Personally I like the 50vmax with bt over benchmark which gives me better than 3,300 fps winter and summer and hits hard. Hope you find something that works good for you.