As it is your truck you can put whatever you want in it.

aftermarket cross members are available for 34" wide frames in many variety of flavors and tastes. From SBC/BBC to most any ford engine series made.

An engine swap requires removal of the bell housing cross member and if it stock was a 292 the front frame mount. 223 six needs no mods as the bracket is not there.

Additionally you will need to add a transmission cross member on the flavor of transmission you want.

Garbz