slant 6 to v8 swap.

Early A ('66 and earlier) cable operated throttle linkage.
Early A engine mount brackets and insulators.
Early A V8 steering center link (slant 6 link is flat, V8 link has a dropped center section for oil pan clearance).
Early A V8 exhaust manifolds.
22" A body V8 radiator compatible with the year engine you're using.
V8 accessory drives for what your car is equipped with (PS, AC, etc.).
V8 (smallblock) transmission.
Heavier torsion bars.
Probably bigger brakes and heavier rear end.
And depending on what year engine/transmission that you want to swap in:
Driveshaft (yours is ball & trunnion, newer ones are slip yoke and U joints).
Different speedo cable.
Different shift linkage and/or steering column (yours is cable operated, newer transmissions are mechanical linkage).
And a whole bunch of other little things.
Lots of threads on this- in the "Early A" forum, use the search button for "V8 swap" and you'll be reading all night long.
BTW, welcome to the site!
:welcome: