What kind of speed from this combination?

[Bumsteer]

I am looking at an R model to buy with a 673A engine, 315 hp, RTO12513 trans, Rockwell single axle 4.33 with a tag.   Any one have any idea what highway speed this would run?  Also any feed back on the 673 engine?  I am not a mack guy just want this for a toy hauler.  It doesn't have power steering but i would assume since it is an r model wouldn't be hard to add. 

[Mark T]

around 70  @2000 RPMs  give or take depending on the rubber and where it's governed at

[Geoff Weeks]

I come up with 67 MPH @ 2100 rpm with 11R22.5 rubber.

If your tires are different, then the top speed will be also.

[67RModel]

17 hours ago, Bumsteer said:

I am looking at an R model to buy with a 673A engine, 315 hp, RTO12513 trans, Rockwell single axle 4.33 with a tag.   Any one have any idea what highway speed this would run?  Also any feed back on the 673 engine?  I am not a mack guy just want this for a toy hauler.  It doesn't have power steering but i would assume since it is an r model wouldn't be hard to add. 

This one? 

1980 Mack R612T - Commercial Vehicles - Wooster, Ohio | Facebook Marketplace | Facebook