I can certainly understand the logistic advantage of commonality of engines, but if you only want vanilla icecream why go to the chocolate chip section?
I am guessing it was either the price or the chance of local production where the American alternative was either too expensive or they were not willing to allow local production.
If that is the case then what they really want is for the Americans to lower their prices or allow local production, so I would expect they will ask for US engines and US sights and US weapons till the Russians say no, but hoping the discussions will push the Americans to change their minds.
If on the other hand they just asked if an American engine was possible on the chance to save a little money by using an existing spare parts pool and existing workforce trained to maintain it.
For the Russians I suspect the point of selling their products is to sell their products and they would likely not want to have to integrate a US engine into such a design, as for most of their clients there is no requirement for US engines.
I am surprised they are not looking at the BTR-82 for a production licence... its anti spall liner and removal of NBC liner make it more practical and of course minor things like single continuous ammo belts for the weapons and improved sighting systems and increased armour probably make it a rather better vehicle without increasing cost too much.