If you knew which Lincoln, that might be helpful. But the number translates to the 351M/400 block. 8H4 is your casting date code, August 4, 1978. That would make it a fairly early 1979 Lincoln, as many engines were installed about 30 days from casting/assembly. There may be tags or decals on the valve covers that might give more clues as to the exact size, 351 or 400.
The only real difference between the two is the stroke/reciprocating assembly. Both engines are 4" bore. The 351 has a 3.5" stroke where the 400 has a 4" stroke. The block, heads, and external bits are the same. If it's apart, or will soon come apart, that's easy enough to check.