The low starting price (I paid $1259 to Jegs on an Ebay special) is about half of what you will need to get thst 260hp - add manifold, carb, headers,(possibly) cast valve covers, dist, water pump, fuel pump, brackets, plug wires & so on & the price can double... If you want a bit more HP & cool factor = more $. I added a modest grind roller cam, roller lifters & rockers, ported the heads & topped it with tri-power. Not a radical change and it's reliable, economical & fun.
Ditto on the bellhousing posts - a repop 3899621 V8 bellhousing (For 168 tooth flywheel, 11" clutch, 4-5/8" bearing retainer) and worked nicely for me. Works with Muncie, Tremec & B-W - I think a T5 works too.