88 Thunderbird

it came with a 3.8 v6 which blew a head gasket last summer. Rather than spending the time and money fixing it, I want to put in a bigger motor. Can anyone tell me what the easiest swap would be. 302 351w/c 429 etc. I would prefer an engine that would bolt right in without major modifications to the motor mounts and / or frame.
Any information will be appreciated
t6hanks
Garry