Dear Inuke;
The 'slightly modified' 261 is the best "all-around" because it bolts right in as mentioned and looks original.
Remember; this emgine is now 185 Hp. which is 100 more than the factory had, runs on regular and requires very little maintance.
The 'later' engines (6 or V-8) require conversions just to fit there, plus your 49 isn't a 49 anymore, It's a 'converted 49' which can be difficult to sell later, depending on the marketplace.
Original "type" vehicles always go up in value and are easy to sell in the future. Simply because they are fewer in number the more conversions are done.
Goodl luck.
