You can get a B-series in without any bending or hammering if you replace the front crossmember.

TWM makes a manifold for DCOE-style carbs, and they also make throttle bodies which are essentially DCOE-style carb replacements. All told, the setup will cost you over two grand.

JG sells bare blocks up to 79mm bore for $650 exchange, or a fully build shortblock for $2295.

Doing up the head will probably cost another $1500 or so with a good port job and cam and such.

So, you're looking at one hella expensive D-series when you can get a B-series for 3 grand tops, spend another grand on installation parts and bolt it all in.