I don't know about Lithuania specifically, but in most (all?) of European countries, doing engine swaps are either outlawed or an administrative nightmare. The "grey card", equivalent of the car title, lists most of the characteristics as weight, HP, displacement, number of seats, outside colour, etc.
Changing one of these characteristics leads to having the title changed and an inspection will be conducted, you'll have to show homologation certificates for everything that is not stock. And you can't hide it because you have mandatory safety inspections at regular intervals.
I put better brakes (the PowerStop kit with bling-bling drilled/slotted rotors, yeah I know) on the Seville. Nope, no way. Had to buy plain rotors in emergency to pass as the maker did not have a certification sheet that certifies these are conform and made for a 1992 Seville.
So yeah, if OP bites the bullet, he may have to stick to the HT4100.