The IRC is not a great tire.....and the rear 140/80-15 is a weird size that is very hard to find.

If you want a rear tire size that is almost identical to the original but gives you far more choices in brands - go with a 130/90-15 tire.  It is almost identical in size to the original and works great on the Savage.

Some folks prefer more meat on the rear tire and run a 140/90-15.  It is a larger diameter tire and weighs more than the stock tire.  That added diameter and helps to make the speedometer more accurate - but the extra weight slows down acceleration a little bit, and helps with straight line stability at the loss of a small amount of quick handling.

The front 100/90-19 is readily available from a lot of tire brands and models.

My favorite affordable tire that gives good performance and decent tread wear is the Shinko 230 Tourmaster.  It is very reasonably priced and handles well in the dry or wet, and it lasts 8,000 - 10,000 miles for most folks.

If you ride a lot of miles you can get the Michelin Commander and it can last 20,000 miles - however that tire is a bit hard and it works great in the dry....but is a bit slippery on wet roads. (It is an expensive tire - but it may be worth the cost if you take a lot of long trips).